{"id":"CVE-2026-83611","aliases":["AZL-99363","CLSA-2026-1788980919","CLSA-2026-1790108624","CLSA-2026-1790755546","CLSA-2026-1790760268","CLSA-2026-1791028067","DEBIAN-CVE-2026-83611","EUVD-2026-69225","GHSA-6h8r-xr42-gp59","UBUNTU-CVE-2026-83611"],"status":"published","title":"xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","severity":{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00619,"percentile":0.50188,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1286"],"published":"2026-09-01T14:34:12Z","modified":"2026-11-05T13:28:23Z","fixes":[{"ecosystem":"npm","package":"@xmldom/xmldom","fixed_in":["0.8.15","0.9.12"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:14","package":"node-xmldom","fixed_in":["0.9.12-1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"@xmldom/xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.7.0"},{"last_affected":"0.8.14"},{"fixed":"0.8.15"}]}]},{"source":"ghsa","ecosystem":"npm","package":"@xmldom/xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.9.0"},{"last_affected":"0.9.11"},{"fixed":"0.9.12"}]}]},{"source":"ghsa","ecosystem":"npm","package":"xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"0.6.0"}]}]},{"source":"osv","ecosystem":"Azure Linux:3","package":"python-tensorboard","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"2.16.2-6"}]}]},{"source":"osv","ecosystem":"TuxCare:npm","package":"xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.6.0-tuxcare.0"},{"fixed":"0.6.0-tuxcare.4"}]}],"versions":["0.6.0","0.6.0-tuxcare.1","0.6.0-tuxcare.2","0.6.0-tuxcare.3"],"bundled":5},{"source":"osv","ecosystem":"TuxCare:npm","package":"xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.1.31-tuxcare.0"},{"fixed":"0.1.31-tuxcare.5"}]}],"versions":["0.1.31","0.1.31-tuxcare.1","0.1.31-tuxcare.2","0.1.31-tuxcare.3","0.1.31-tuxcare.4"],"bundled":5},{"source":"osv","ecosystem":"TuxCare:npm","package":"@xmldom/xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.7.13-tuxcare.0"},{"fixed":"0.7.13-tuxcare.1"}]}],"versions":["0.7.13"],"bundled":14},{"source":"osv","ecosystem":"TuxCare:npm","package":"@xmldom/xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.9.10-tuxcare.0"},{"fixed":"0.9.10-tuxcare.2"}]}],"versions":["0.9.10","0.9.10-tuxcare.1"],"bundled":4},{"source":"osv","ecosystem":"TuxCare:npm","package":"@xmldom/xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.9.8-tuxcare.0"},{"fixed":"0.9.8-tuxcare.1"}]}],"versions":["0.9.8"],"bundled":3},{"source":"osv","ecosystem":"Debian:12","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.6-1","0.9.10-1","0.9.10-2","0.9.11-1","0.9.12-1","0.9.5-1","0.9.6-1","0.9.8-1","0.9.8-2","0.9.9-1"]},{"source":"osv","ecosystem":"Debian:13","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.9.10-1","0.9.10-2","0.9.11-1","0.9.12-1","0.9.6-1","0.9.8-1","0.9.8-2","0.9.9-1"]},{"source":"osv","ecosystem":"Debian:14","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.12-1"}]}],"versions":["0.9.10-1","0.9.10-2","0.9.11-1","0.9.6-1","0.9.8-1","0.9.8-2","0.9.9-1"]},{"source":"osv","ecosystem":"npm","package":"@xmldom/xmldom","ranges":[{"type":"SEMVER","events":[{"introduced":"0.7.0"},{"fixed":"0.8.15"}]}]},{"source":"osv","ecosystem":"npm","package":"@xmldom/xmldom","ranges":[{"type":"SEMVER","events":[{"introduced":"0.9.0"},{"fixed":"0.9.12"}]}]},{"source":"osv","ecosystem":"npm","package":"xmldom","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"last_affected":"0.6.0"}]}]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.1.27+ds-1","0.1.27+ds-1+deb10u2build0.20.04.1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.5.0-1","0.7.3-1","0.7.5-1","0.7.5-1ubuntu0.22.04.1"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.6-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.9.8-2","0.9.10-2","0.9.11-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"node-xmldom","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.9.6-1","0.9.8-1","0.9.8-2"]}],"products":[{"vendor":"@xmldom","product":"xmldom"},{"vendor":"xmldom","product":"xmldom"}],"references":[{"url":"https://github.com/xmldom/xmldom/security/advisories/GHSA-6h8r-xr42-gp59","tags":["x_refsource_CONFIRM","exploit","advisory","web","report"]},{"url":"https://github.com/xmldom/xmldom/pull/1071","tags":["x_refsource_MISC","fix","web","report"]},{"url":"https://github.com/xmldom/xmldom/pull/1072","tags":["x_refsource_MISC","fix","web","report"]},{"url":"https://github.com/xmldom/xmldom/commit/4430189660b0d380ee9c9ee7550a1358688e8828","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/xmldom/xmldom/commit/7b2ec67e1750daadd0bb06c92e875e726544a362","tags":["x_refsource_MISC","fix","web"]},{"url":"https://github.com/xmldom/xmldom/releases/tag/0.8.15","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/xmldom/xmldom/releases/tag/0.9.12","tags":["x_refsource_MISC","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-83611","tags":["web","advisory"]},{"url":"https://github.com/advisories/GHSA-6h8r-xr42-gp59"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/83xxx/CVE-2026-83611.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-83611","tags":["advisory"]},{"url":"https://github.com/xmldom/xmldom","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2026-83611","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-83611","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-83611","title":"xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","status":"published","published":"2026-09-01T14:34:12.618Z","modified":"2026-09-01T14:53:37.513Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium","assessor":"cna"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T13:45:02.910572Z"}],"euvd":[{"id":"EUVD-2026-69225","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","status":"published","published":"2026-09-01T14:34:12Z","modified":"2026-09-01T14:53:37Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T18:01:18.264709Z"}],"ghsa":[{"id":"GHSA-6h8r-xr42-gp59","title":"xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content","description":"## Summary\n\nxmldom's parser silently accepts a **not-well-formed end tag** whose valid name is followed by\ntrailing content — e.g. `\u003c/a⏎junk\u003e`. The element is closed, the trailing content is discarded, and no\nerror is reported, even though the XML end-tag production allows only optional whitespace after the\nname and both Chromium and Firefox reject such input as `application/xml`. An application that relies\non xmldom to reject not-well-formed input therefore receives a false \"valid\" result for a document the\nspecification and browsers consider malformed.\n\n## Details\n\nAcross every affected version, an end tag whose valid `Name` is followed by trailing content before\n`\u003e` is silently accepted: the element is closed, the residue is dropped, and no error is reported. How\nmuch leaks differs by line (see Affected Versions), but the observable weakness is the same.\n\nOn the current (`0.9.x`) line, the parser validates the end-tag name against the XML `ETag` production\nwith an anchored regular expression (`^ QName S? $`). That expression is compiled with the `m`\n(multiline) flag by a shared builder, so `$` matches at an interior line terminator: a valid name on\nthe first line satisfies the anchored production and any content after the line break escapes the\ncheck. On 0.9.x the whitespace-separated variant (`\u003c/a junk\u003e`) is already rejected; only the\nline-terminator variant leaks. Older lines have no anchored end-tag validator at all, so they accept\nboth the line-terminator and the whitespace variant.\n\nThis is **not** content injection — the trailing content is dropped, and the resulting DOM is a normal\nsingle-root document (`\u003ca/\u003e`). The security-relevant property is the silent acceptance of\nnot-well-formed input: xmldom's parse result disagrees with the specification and with browser XML\nparsers, so any control that treats \"xmldom parsed it without error\" as \"well-formed\" is bypassed.\n\n### Root Cause\n\nOn the `0.9.x` line, where the line-terminator variant specifically leaks:\n\n1. A shared regexp builder compiles anchored productions with the `m` flag.\n2. `^…$` under `m` are line anchors, not string anchors.\n3. The anchored end-tag production `^ QName S? $` is therefore satisfied by the first line alone, so\n   trailing content after a line terminator is neither matched nor rejected — the malformed end tag is\n   accepted and the residue silently discarded.\n\nThe triggering line terminators are the ECMAScript `LineTerminator` set: U+000A, U+000D, U+2028, U+2029.\nU+2028 and U+2029 are not XML whitespace, so they are non-conforming trailing content that nonetheless\nleaks because the JavaScript `$` anchor treats them as line boundaries under `m`.\n\n## Affected Versions\n\nBoth maintained versions are affected and fixed:\n\n- **`0.9.x`** (`\u003e= 0.9.0, \u003c= 0.9.11`) → **`0.9.12`**: the anchored end-tag validator's `m` flag leaks\n  the line-terminator variant. The whitespace variant (`\u003c/a junk\u003e`) is already rejected on this line.\n- **`0.8.x`** (`\u003e= 0.8.0, \u003c= 0.8.14`) → **`0.8.15`**: no anchored end-tag validator at all — both the\n  line-terminator and the whitespace variant are silently accepted; the fix adds a residue check.\n\n`release-0.7.x` (`\u003c= 0.7.13`) and the unscoped `xmldom` package (range `*`, last release 0.6.0) are\n**affected but will not be patched** — they are end-of-life / unmaintained. They share the older-line\nbehavior (both variants silently accepted, residue dropped).\n\n## Proof of Concept\n\n```js\nconst { DOMParser, XMLSerializer } = require('@xmldom/xmldom');\nconst doc = new DOMParser().parseFromString('\u003ca\u003e\u003c/a\\njunk\u003e', 'text/xml'); // no error\nconsole.log(new XMLSerializer().serializeToString(doc));\n// Observed: \u003ca/\u003e   — the malformed end tag is accepted, \"junk\" silently discarded, no error reported.\n// Expected (per XML spec / Chromium / Firefox): a parse error — the input is not well-formed.\n```\n\n## Impact\n\n- **Silent acceptance of not-well-formed XML**: a document the specification and browser XML parsers\n  reject is parsed without error.\n- **Bypass of a well-formedness / parse-before-trust gate**: an application relying on xmldom to\n  reject malformed input treats such a document as valid. Note this is an input-validation /\n  parser-differential issue, not content injection — the trailing content is discarded.\n\n## Fix Applied\n\nThe parser now reports a not-well-formed end tag whose valid name is followed by trailing content, on both `0.9.12` and `0.8.15` — previously it was accepted silently — and parsing recovers to the byte-identical DOM as before.\\\nOn `0.9.12` the anchored end-tag validator is corrected so a line break followed by trailing content no longer satisfies it, reported as a recoverable `error` when parsing as XML and a `warning` when parsing as HTML.\\\nOn `0.8.15`, which previously performed no end-tag residue validation, an equivalent residue check is added, reported as a recoverable `error` in both XML and HTML.\\\nWell-formed documents are unaffected.\n\nBecause the report is recoverable, the fix is non-breaking: no previously-parsed document begins to\nthrow and no serialized output changes. Consumers that want strict rejection can escalate the reported\n`error` to a fatal one via the parser's error handler (`onError` in `0.9.12`, `errorHandler` in\n`0.8.15`). The two versions also differ in the whitespace-separated variant (`\u003c/a junk\u003e`): `0.9.12`\nalready rejected it with a fatal error in XML and continues to, while `0.8.15` — which validated\nneither variant — now emits the same recoverable report for both the whitespace and line-break\nvariants.\n\n### Residual limitation\n\nBy default the parser still **recovers** (it does not reject the document); the reported condition is a\nrecoverable `error`/`warning`, not a fatal error, to avoid changing the parsed output in a patch\nrelease. Converting this and the other not-well-formed-acceptance cases to a consistent `fatalError` —\nincluding the broader end-tag leniency on the older versions — is deferred to the next breaking release,\ntracked at [xmldom/xmldom#1074](https://github.com/xmldom/xmldom/issues/1074).","status":"published","published":"2026-09-08T21:02:13Z","modified":"2026-09-08T21:02:13Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T14:41:14.764963Z"}],"nvd":[{"id":"CVE-2026-83611","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","status":"published","published":"2026-09-01T15:17:39.263Z","modified":"2026-09-08T21:11:31.703Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T14:12:43.04945Z"}],"osv":[{"id":"CVE-2026-83611","title":"xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","status":"published","published":"2026-09-01T14:34:12.618Z","modified":"2026-11-11T02:49:06.706674238Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-1286"],"updated_at":"2026-11-11T03:21:16.313764Z"},{"id":"DEBIAN-CVE-2026-83611","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","status":"published","published":"2026-09-01T15:17:39.263Z","modified":"2026-10-01T03:03:43.249011278Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium"}],"updated_at":"2026-11-02T15:46:04.577397Z"},{"id":"GHSA-6h8r-xr42-gp59","title":"xmldom: Parser silently accepts a not-well-formed end tag whose name is followed by a line break and trailing content","description":"## Summary\n\nxmldom's parser silently accepts a **not-well-formed end tag** whose valid name is followed by\ntrailing content — e.g. `\u003c/a⏎junk\u003e`. The element is closed, the trailing content is discarded, and no\nerror is reported, even though the XML end-tag production allows only optional whitespace after the\nname and both Chromium and Firefox reject such input as `application/xml`. An application that relies\non xmldom to reject not-well-formed input therefore receives a false \"valid\" result for a document the\nspecification and browsers consider malformed.\n\n## Details\n\nAcross every affected version, an end tag whose valid `Name` is followed by trailing content before\n`\u003e` is silently accepted: the element is closed, the residue is dropped, and no error is reported. How\nmuch leaks differs by line (see Affected Versions), but the observable weakness is the same.\n\nOn the current (`0.9.x`) line, the parser validates the end-tag name against the XML `ETag` production\nwith an anchored regular expression (`^ QName S? $`). That expression is compiled with the `m`\n(multiline) flag by a shared builder, so `$` matches at an interior line terminator: a valid name on\nthe first line satisfies the anchored production and any content after the line break escapes the\ncheck. On 0.9.x the whitespace-separated variant (`\u003c/a junk\u003e`) is already rejected; only the\nline-terminator variant leaks. Older lines have no anchored end-tag validator at all, so they accept\nboth the line-terminator and the whitespace variant.\n\nThis is **not** content injection — the trailing content is dropped, and the resulting DOM is a normal\nsingle-root document (`\u003ca/\u003e`). The security-relevant property is the silent acceptance of\nnot-well-formed input: xmldom's parse result disagrees with the specification and with browser XML\nparsers, so any control that treats \"xmldom parsed it without error\" as \"well-formed\" is bypassed.\n\n### Root Cause\n\nOn the `0.9.x` line, where the line-terminator variant specifically leaks:\n\n1. A shared regexp builder compiles anchored productions with the `m` flag.\n2. `^…$` under `m` are line anchors, not string anchors.\n3. The anchored end-tag production `^ QName S? $` is therefore satisfied by the first line alone, so\n   trailing content after a line terminator is neither matched nor rejected — the malformed end tag is\n   accepted and the residue silently discarded.\n\nThe triggering line terminators are the ECMAScript `LineTerminator` set: U+000A, U+000D, U+2028, U+2029.\nU+2028 and U+2029 are not XML whitespace, so they are non-conforming trailing content that nonetheless\nleaks because the JavaScript `$` anchor treats them as line boundaries under `m`.\n\n## Affected Versions\n\nBoth maintained versions are affected and fixed:\n\n- **`0.9.x`** (`\u003e= 0.9.0, \u003c= 0.9.11`) → **`0.9.12`**: the anchored end-tag validator's `m` flag leaks\n  the line-terminator variant. The whitespace variant (`\u003c/a junk\u003e`) is already rejected on this line.\n- **`0.8.x`** (`\u003e= 0.8.0, \u003c= 0.8.14`) → **`0.8.15`**: no anchored end-tag validator at all — both the\n  line-terminator and the whitespace variant are silently accepted; the fix adds a residue check.\n\n`release-0.7.x` (`\u003c= 0.7.13`) and the unscoped `xmldom` package (range `*`, last release 0.6.0) are\n**affected but will not be patched** — they are end-of-life / unmaintained. They share the older-line\nbehavior (both variants silently accepted, residue dropped).\n\n## Proof of Concept\n\n```js\nconst { DOMParser, XMLSerializer } = require('@xmldom/xmldom');\nconst doc = new DOMParser().parseFromString('\u003ca\u003e\u003c/a\\njunk\u003e', 'text/xml'); // no error\nconsole.log(new XMLSerializer().serializeToString(doc));\n// Observed: \u003ca/\u003e   — the malformed end tag is accepted, \"junk\" silently discarded, no error reported.\n// Expected (per XML spec / Chromium / Firefox): a parse error — the input is not well-formed.\n```\n\n## Impact\n\n- **Silent acceptance of not-well-formed XML**: a document the specification and browser XML parsers\n  reject is parsed without error.\n- **Bypass of a well-formedness / parse-before-trust gate**: an application relying on xmldom to\n  reject malformed input treats such a document as valid. Note this is an input-validation /\n  parser-differential issue, not content injection — the trailing content is discarded.\n\n## Fix Applied\n\nThe parser now reports a not-well-formed end tag whose valid name is followed by trailing content, on both `0.9.12` and `0.8.15` — previously it was accepted silently — and parsing recovers to the byte-identical DOM as before.\\\nOn `0.9.12` the anchored end-tag validator is corrected so a line break followed by trailing content no longer satisfies it, reported as a recoverable `error` when parsing as XML and a `warning` when parsing as HTML.\\\nOn `0.8.15`, which previously performed no end-tag residue validation, an equivalent residue check is added, reported as a recoverable `error` in both XML and HTML.\\\nWell-formed documents are unaffected.\n\nBecause the report is recoverable, the fix is non-breaking: no previously-parsed document begins to\nthrow and no serialized output changes. Consumers that want strict rejection can escalate the reported\n`error` to a fatal one via the parser's error handler (`onError` in `0.9.12`, `errorHandler` in\n`0.8.15`). The two versions also differ in the whitespace-separated variant (`\u003c/a junk\u003e`): `0.9.12`\nalready rejected it with a fatal error in XML and continues to, while `0.8.15` — which validated\nneither variant — now emits the same recoverable report for both the whitespace and line-break\nvariants.\n\n### Residual limitation\n\nBy default the parser still **recovers** (it does not reject the document); the reported condition is a\nrecoverable `error`/`warning`, not a fatal error, to avoid changing the parsed output in a patch\nrelease. Converting this and the other not-well-formed-acceptance cases to a consistent `fatalError` —\nincluding the broader end-tag leniency on the older versions — is deferred to the next breaking release,\ntracked at [xmldom/xmldom#1074](https://github.com/xmldom/xmldom/issues/1074).","status":"published","published":"2026-09-08T21:02:13Z","modified":"2026-09-08T21:15:03.934672343Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"cwes":["CWE-1286"],"updated_at":"2026-11-02T15:46:39.618611Z"},{"id":"UBUNTU-CVE-2026-83611","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","status":"published","published":"2026-09-01T15:17:00Z","modified":"2026-10-17T13:01:11.849071177Z","cvss":[{"version":"4.0","score":6.9,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","level":"medium"}],"updated_at":"2026-11-02T16:57:22.213888Z"},{"id":"AZL-99363","title":"CVE-2026-83611 affecting package python-tensorboard 2.16.2-6","description":"xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions 0.8.15 and 0.9.12, and in xmldom version 0.6.0 and earlier, DOMParser.parseFromString() can silently accept an end tag such as \u003c/a\\njunk\u003e, close the element, and discard the trailing content. On 0.9.x, the lib/sax.js end-tag validator inherits the multiline flag from reg(), allowing the first line to satisfy the anchored XML ETag production; older lines have no equivalent residue validation. This parser differential can bypass a parse-before-trust well-formedness gate, although it does not inject the discarded content; onError on 0.9.x and errorHandler on 0.8.x are the relevant reporting interfaces. This issue is fixed in @xmldom/xmldom versions 0.8.15 and 0.9.12; no fixed version is available for xmldom.","status":"published","published":"2026-09-01T15:17:39Z","modified":"2026-09-08T05:27:28Z","updated_at":"2026-11-02T15:28:12.596039Z"},{"id":"CLSA-2026-1788980919","title":"TuxCare security update for xmldom (5 CVEs)","description":"TuxCare rebuilt xmldom to address 5 CVEs. Fixed in 0.6.0-tuxcare.4.","status":"published","published":"2026-09-09T19:08:39Z","modified":"2026-10-15T09:47:56.142670074Z","updated_at":"2026-11-02T15:43:47.938828Z"},{"id":"CLSA-2026-1790108624","title":"TuxCare security update for xmldom (5 CVEs)","description":"TuxCare rebuilt xmldom to address 5 CVEs. Fixed in 0.1.31-tuxcare.5.","status":"published","published":"2026-09-22T20:23:44Z","modified":"2026-11-05T13:28:23.742251042Z","updated_at":"2026-11-05T16:37:45.64821Z"},{"id":"CLSA-2026-1790755546","title":"TuxCare security update for @xmldom/xmldom (14 CVEs)","description":"TuxCare rebuilt @xmldom/xmldom to address 14 CVEs. Fixed in 0.7.13-tuxcare.1.","status":"published","published":"2026-09-30T08:05:46Z","modified":"2026-10-15T09:47:53.549832566Z","updated_at":"2026-11-02T15:43:48.65893Z"},{"id":"CLSA-2026-1790760268","title":"TuxCare security update for @xmldom/xmldom (4 CVEs)","description":"TuxCare rebuilt @xmldom/xmldom to address 4 CVEs. Fixed in 0.9.10-tuxcare.2.","status":"published","published":"2026-09-30T09:24:28Z","modified":"2026-10-15T09:47:57.301956488Z","updated_at":"2026-11-02T15:43:48.65893Z"},{"id":"CLSA-2026-1791028067","title":"TuxCare security update for @xmldom/xmldom (3 CVEs)","description":"TuxCare rebuilt @xmldom/xmldom to address 3 CVEs. Fixed in 0.9.8-tuxcare.1.","status":"published","published":"2026-10-03T11:47:47Z","modified":"2026-10-15T09:47:38.622375059Z","updated_at":"2026-11-02T15:43:49.016976Z"}]}}