{"id":"CVE-2026-59925","aliases":["AZL-92217","DEBIAN-CVE-2026-59925","EUVD-2026-42335","GHSA-4j32-57v6-6g45","PYSEC-2026-2213","SUSE-SU-2026:22655-1","UBUNTU-CVE-2026-59925","openSUSE-SU-2026:21339-1"],"status":"published","title":"inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00644,"percentile":0.51331,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-1333","CWE-407"],"published":"2026-07-08T16:18:43Z","modified":"2026-11-11T09:40:07Z","fixes":[{"ecosystem":"PyPI","package":"mistune","fixed_in":["3.3.0"],"sources":["ghsa","osv"]},{"ecosystem":"Azure Linux:3","package":"python-mistune","fixed_in":["3.3.0-1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.3.0"}]}]},{"source":"osv","ecosystem":"Azure Linux:3","package":"python-mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.3.0-1"}]}]},{"source":"osv","ecosystem":"Debian:13","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.3-1","3.1.4-1","3.3.4-1","3.4.0-1"]},{"source":"osv","ecosystem":"Debian:14","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.3-1","3.1.4-1","3.3.4-1","3.4.0-1"]},{"source":"osv","ecosystem":"PyPI","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.3.0"}]}],"versions":["0.1.0","0.2.0","0.3.0","0.3.1","0.4","0.4.1","0.5","0.5.1","0.6","0.7","0.7.1","0.7.2","0.7.3","0.7.4","0.8","0.8.1","0.8.2","0.8.3","0.8.4","2.0.0","2.0.0a1","2.0.0a2","2.0.0a3","2.0.0a4","2.0.0a5","2.0.0a6","2.0.0rc1","2.0.1","2.0.2","2.0.3","2.0.4","2.0.5","2.1.0","3.0.0","3.0.0a1","3.0.0a2","3.0.0a3","3.0.0rc1","3.0.0rc2","3.0.0rc3","3.0.0rc4","3.0.0rc5","3.0.1","3.0.2","3.1.0","3.1.1","3.1.2","3.1.3","3.1.4","3.2.0","3.2.1"]},{"source":"osv","ecosystem":"PyPI","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.3.0"}]}],"versions":["0.1.0","0.2.0","0.3.0","0.3.1","0.4","0.4.1","0.5","0.5.1","0.6","0.7","0.7.1","0.7.2","0.7.3","0.7.4","0.8","0.8.1","0.8.2","0.8.3","0.8.4","2.0.0","2.0.0a1","2.0.0a2","2.0.0a3","2.0.0a4","2.0.0a5","2.0.0a6","2.0.0rc1","2.0.1","2.0.2","2.0.3","2.0.4","2.0.5","2.1.0","3.0.0","3.0.0a1","3.0.0a2","3.0.0a3","3.0.0rc1","3.0.0rc2","3.0.0rc3","3.0.0rc4","3.0.0rc5","3.0.1","3.0.2","3.1.0","3.1.1","3.1.2","3.1.3","3.1.4","3.2.0","3.2.1"]},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server 16.0","package":"python-mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.3-160000.5.1"}]}],"bundled":10},{"source":"osv","ecosystem":"SUSE:Linux Enterprise Server for SAP applications 16.0","package":"python-mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.3-160000.5.1"}]}],"bundled":10},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6-2","0.7.1-1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.7.4-1","0.8-1","0.8.1-1","0.8.3-2"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.8.4-1","0.8.4-2"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.4-2","3.0.2-1"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.2-2","3.1.3-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.4-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.1.3-1","3.1.4-1"]},{"source":"osv","ecosystem":"openSUSE:Leap 16.0","package":"python-mistune","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.3-160000.5.1"}]}],"bundled":10}],"products":[{"vendor":"lepture","product":"mistune"},{"vendor":"mistune_project","product":"mistune"}],"references":[{"url":"https://github.com/lepture/mistune/security/advisories/GHSA-4j32-57v6-6g45","tags":["x_refsource_CONFIRM","Exploit","Vendor Advisory","advisory","web","evidence","report"]},{"url":"https://github.com/lepture/mistune/commit/5de41fb8e527004dbc363e047a3c380c9288c74f","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/lepture/mistune/releases/tag/v3.3.0","tags":["x_refsource_MISC","Release Notes","web","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59925","tags":["web","advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2213.yaml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-4j32-57v6-6g45"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59925.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-59925","tags":["advisory"]},{"url":"https://github.com/lepture/mistune","tags":["package"]},{"url":"https://www.suse.com/support/update/announcement/2026/suse-su-202622655-1/","tags":["advisory"]},{"url":"https://bugzilla.suse.com/1271082","tags":["report"]},{"url":"https://bugzilla.suse.com/1271117","tags":["report"]},{"url":"https://bugzilla.suse.com/1271119","tags":["report"]},{"url":"https://bugzilla.suse.com/1271121","tags":["report"]},{"url":"https://bugzilla.suse.com/1271125","tags":["report"]},{"url":"https://bugzilla.suse.com/1271127","tags":["report"]},{"url":"https://bugzilla.suse.com/1271128","tags":["report"]},{"url":"https://bugzilla.suse.com/1271131","tags":["report"]},{"url":"https://bugzilla.suse.com/1271132","tags":["report"]},{"url":"https://www.suse.com/security/cve/CVE-2026-44896","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59922","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59923","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59924","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59925","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59926","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59927","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59928","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59929","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2026-59930","tags":["web"]},{"url":"https://ubuntu.com/security/CVE-2026-59925","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-59925","tags":["report"]},{"url":"","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-59925","title":"inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T16:18:43.786Z","modified":"2026-07-08T19:44:48.084Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-407","CWE-1333"],"updated_at":"2026-11-02T14:19:58.944663Z"}],"euvd":[{"id":"EUVD-2026-42335","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T16:18:43Z","modified":"2026-07-08T19:44:48Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T18:20:10.095263Z"}],"ghsa":[{"id":"GHSA-4j32-57v6-6g45","title":"Mistune inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs","description":"## Summary\n\n**Type:** Algorithmic-complexity DoS in core emphasis parsing. A long sequence of well-formed `**x**` (strong) or `***x***` (strong-emphasis combined) pairs causes O(N²) parser work. Distinct from the bracket-bomb DoS (`[` repetition) and from the formatting-plugin DoS (`~~`/`==`/`^^`); this one fires on default-config mistune with no plugins required.\n**File:** `src/mistune/inline_parser.py` lines 41-48 (the `EMPHASIS_END_RE` family) and the surrounding emphasis dispatch.\n**Root cause:** for every opening run of `*`s the parser scans forward using one of `EMPHASIS_END_RE['*']` / `['**']` / `['***']` to find the matching close. Each scan is bounded per call, but the parser invokes the scan from every potential start position. For input shaped `**x**` repeated N times, every `**` is treated as a potential start, each scan can cover up to the end of input. Total work is O(N²). The triple-emphasis variant `***x***` is slightly worse due to the extra alternation between `*`, `**`, and `***` close patterns. Reproducible against default mistune with no plugins.\n\n## Affected Code\n\n**File:** `src/mistune/inline_parser.py`, lines 41-48.\n\n```python\nEMPHASIS_END_RE = {\n    \"*\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\\\*|[^\\s*])\\*(?!\\*)\"),\n    \"_\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\_|[^\\s_])_(?!_)\\b\"),\n    \"**\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\\\*|[^\\s*])\\*\\*(?!\\*)\"),\n    \"__\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\_|[^\\s_])__(?!_)\\b\"),\n    \"***\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\\\*|[^\\s*])\\*\\*\\*(?!\\*)\"),\n    \"___\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\_|[^\\s_])___(?!_)\\b\"),\n}\n# Each of the six end-patterns is invoked from every emphasis open position\n# fired by the inline rule `r\"\\*{1,3}(?=[^\\s*])|\\b_{1,3}(?=[^\\s_])\"`. The\n# scan itself is bounded per call; the cost comes from the parser invoking\n# the scan at every matching open marker, giving O(N²) total work.\n```\n\n**Why it's wrong:** same shape as the formatting-plugin and bracket-bomb DoS findings. The CommonMark reference parser handles emphasis in linear time using a delimiter-stack algorithm (`commonmark.js`, `commonmark-py`, `markdown-it-py` all do this). mistune retries the close-scan from each open marker. The bounded regex is not enough; the surrounding loop is the source of the quadratic.\n\n## Exploit Chain\n\n1. Application uses mistune to render user-supplied markdown. No plugins required — affects the default `mistune.create_markdown()` configuration.\n2. Attacker submits a 40 KB payload of `**x**` repeated 8000 times.\n3. Server CPU pegs for ~4 seconds; 16 KB → ~17 seconds. Doubling input quadruples time.\n4. Repeating the request floods the worker pool.\n\n## Security Impact\n\n**Severity:** sec-high. Network-reachable, no authentication, no plugin requirement. Default mistune is vulnerable.\n**Attacker capability:** O(N²) CPU cost from a single small input. Predictable scaling, easy to combine with concurrent requests for service denial.\n**Preconditions:** application uses `mistune.create_markdown()` (default config) on attacker-supplied markdown. No plugins required.\n**Differential:** PoC-verified against mistune@3.2.1, default config:\n\n```python\nimport mistune, time\nmd = mistune.create_markdown()                     # no plugins\nfor n in [500, 1000, 2000, 4000, 8000]:\n    s = '**x**' * n\n    t = time.time()\n    md(s)\n    print(f'  **x** * {n} ({len(s)}b): {(time.time() - t) * 1000:.0f}ms')\n\n# Output (Python 3.13, Linux, 2.5GHz CPU):\n#   **x** *  500  (2500b):    20ms\n#   **x** * 1000  (5000b):    74ms\n#   **x** * 2000 (10000b):   284ms\n#   **x** * 4000 (20000b):  1079ms\n#   **x** * 8000 (40000b):  4309ms\n\n# Triple-emphasis is similar:\nmd('***x***' * 4000)   # ~1500ms\n\n# Linear in N for non-emphasis input of comparable size:\nmd('xxxxx' * 8000)     # 1ms (4000x faster)\n```\n\nThe patched build (with the suggested fix below — delimiter-stack rewrite or hard cap on simultaneous open markers) keeps the time linear in N.\n\n## Suggested Fix\n\nCap the number of unmatched opening emphasis markers the parser will track simultaneously, treating the rest as literal text:\n\n```diff\n--- a/src/mistune/inline_parser.py\n+++ b/src/mistune/inline_parser.py\n@@ ... in the emphasis-handling code path\n+    # Bound the number of open emphasis markers tracked. CommonMark gives\n+    # no semantics to deeply nested unmatched emphasis; this cap turns the\n+    # parser-level O(N^2) into O(N) for adversarial inputs while preserving\n+    # behaviour on every realistic markdown document.\n+    MAX_OPEN_EMPHASIS = 100\n+    if open_emphasis_count \u003e MAX_OPEN_EMPHASIS:\n+        # treat remaining * / _ as literal text\n+        ...\n```\n\nThe proper fix is a delimiter-stack pass, the same approach the formatting-plugin advisory and the bracket-bomb advisory recommend. All three DoS findings share the same algorithmic pattern; a single rewrite of the inline-token retry loop closes them together. Add a regression test asserting that `md('**x**' * 50_000)` completes in under 1 second.","status":"published","published":"2026-07-20T21:32:40Z","modified":"2026-07-20T21:32:42Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-407","CWE-1333"],"updated_at":"2026-11-02T14:40:48.410776Z"}],"nvd":[{"id":"CVE-2026-59925","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T17:17:28.183Z","modified":"2026-10-25T17:10:00.197Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"}],"cwes":["CWE-407","CWE-1333"],"updated_at":"2026-11-02T14:12:28.4135Z"}],"osv":[{"id":"CVE-2026-59925","title":"inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T16:18:43.786Z","modified":"2026-10-28T02:30:34.207731278Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-1333","CWE-407"],"updated_at":"2026-11-02T15:45:12.496548Z"},{"id":"DEBIAN-CVE-2026-59925","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T17:17:28.183Z","modified":"2026-10-26T12:02:38.42946404Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:45:57.932517Z"},{"id":"GHSA-4j32-57v6-6g45","title":"Mistune inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs","description":"## Summary\n\n**Type:** Algorithmic-complexity DoS in core emphasis parsing. A long sequence of well-formed `**x**` (strong) or `***x***` (strong-emphasis combined) pairs causes O(N²) parser work. Distinct from the bracket-bomb DoS (`[` repetition) and from the formatting-plugin DoS (`~~`/`==`/`^^`); this one fires on default-config mistune with no plugins required.\n**File:** `src/mistune/inline_parser.py` lines 41-48 (the `EMPHASIS_END_RE` family) and the surrounding emphasis dispatch.\n**Root cause:** for every opening run of `*`s the parser scans forward using one of `EMPHASIS_END_RE['*']` / `['**']` / `['***']` to find the matching close. Each scan is bounded per call, but the parser invokes the scan from every potential start position. For input shaped `**x**` repeated N times, every `**` is treated as a potential start, each scan can cover up to the end of input. Total work is O(N²). The triple-emphasis variant `***x***` is slightly worse due to the extra alternation between `*`, `**`, and `***` close patterns. Reproducible against default mistune with no plugins.\n\n## Affected Code\n\n**File:** `src/mistune/inline_parser.py`, lines 41-48.\n\n```python\nEMPHASIS_END_RE = {\n    \"*\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\\\*|[^\\s*])\\*(?!\\*)\"),\n    \"_\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\_|[^\\s_])_(?!_)\\b\"),\n    \"**\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\\\*|[^\\s*])\\*\\*(?!\\*)\"),\n    \"__\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\_|[^\\s_])__(?!_)\\b\"),\n    \"***\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\\\*|[^\\s*])\\*\\*\\*(?!\\*)\"),\n    \"___\": re.compile(r\"(?:\" + PREVENT_BACKSLASH + r\"\\\\_|[^\\s_])___(?!_)\\b\"),\n}\n# Each of the six end-patterns is invoked from every emphasis open position\n# fired by the inline rule `r\"\\*{1,3}(?=[^\\s*])|\\b_{1,3}(?=[^\\s_])\"`. The\n# scan itself is bounded per call; the cost comes from the parser invoking\n# the scan at every matching open marker, giving O(N²) total work.\n```\n\n**Why it's wrong:** same shape as the formatting-plugin and bracket-bomb DoS findings. The CommonMark reference parser handles emphasis in linear time using a delimiter-stack algorithm (`commonmark.js`, `commonmark-py`, `markdown-it-py` all do this). mistune retries the close-scan from each open marker. The bounded regex is not enough; the surrounding loop is the source of the quadratic.\n\n## Exploit Chain\n\n1. Application uses mistune to render user-supplied markdown. No plugins required — affects the default `mistune.create_markdown()` configuration.\n2. Attacker submits a 40 KB payload of `**x**` repeated 8000 times.\n3. Server CPU pegs for ~4 seconds; 16 KB → ~17 seconds. Doubling input quadruples time.\n4. Repeating the request floods the worker pool.\n\n## Security Impact\n\n**Severity:** sec-high. Network-reachable, no authentication, no plugin requirement. Default mistune is vulnerable.\n**Attacker capability:** O(N²) CPU cost from a single small input. Predictable scaling, easy to combine with concurrent requests for service denial.\n**Preconditions:** application uses `mistune.create_markdown()` (default config) on attacker-supplied markdown. No plugins required.\n**Differential:** PoC-verified against mistune@3.2.1, default config:\n\n```python\nimport mistune, time\nmd = mistune.create_markdown()                     # no plugins\nfor n in [500, 1000, 2000, 4000, 8000]:\n    s = '**x**' * n\n    t = time.time()\n    md(s)\n    print(f'  **x** * {n} ({len(s)}b): {(time.time() - t) * 1000:.0f}ms')\n\n# Output (Python 3.13, Linux, 2.5GHz CPU):\n#   **x** *  500  (2500b):    20ms\n#   **x** * 1000  (5000b):    74ms\n#   **x** * 2000 (10000b):   284ms\n#   **x** * 4000 (20000b):  1079ms\n#   **x** * 8000 (40000b):  4309ms\n\n# Triple-emphasis is similar:\nmd('***x***' * 4000)   # ~1500ms\n\n# Linear in N for non-emphasis input of comparable size:\nmd('xxxxx' * 8000)     # 1ms (4000x faster)\n```\n\nThe patched build (with the suggested fix below — delimiter-stack rewrite or hard cap on simultaneous open markers) keeps the time linear in N.\n\n## Suggested Fix\n\nCap the number of unmatched opening emphasis markers the parser will track simultaneously, treating the rest as literal text:\n\n```diff\n--- a/src/mistune/inline_parser.py\n+++ b/src/mistune/inline_parser.py\n@@ ... in the emphasis-handling code path\n+    # Bound the number of open emphasis markers tracked. CommonMark gives\n+    # no semantics to deeply nested unmatched emphasis; this cap turns the\n+    # parser-level O(N^2) into O(N) for adversarial inputs while preserving\n+    # behaviour on every realistic markdown document.\n+    MAX_OPEN_EMPHASIS = 100\n+    if open_emphasis_count \u003e MAX_OPEN_EMPHASIS:\n+        # treat remaining * / _ as literal text\n+        ...\n```\n\nThe proper fix is a delimiter-stack pass, the same approach the formatting-plugin advisory and the bracket-bomb advisory recommend. All three DoS findings share the same algorithmic pattern; a single rewrite of the inline-token retry loop closes them together. Add a regression test asserting that `md('**x**' * 50_000)` completes in under 1 second.","status":"published","published":"2026-07-20T21:32:40Z","modified":"2026-07-20T21:46:43.348949802Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-1333","CWE-407"],"updated_at":"2026-11-02T15:46:37.148947Z"},{"id":"PYSEC-2026-2213","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T17:17:28.183Z","modified":"2026-07-13T07:15:18.858108495Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-02T15:52:55.537808Z"},{"id":"UBUNTU-CVE-2026-59925","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T17:17:00Z","modified":"2026-11-11T09:40:07.670637386Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-11T10:02:12.942344Z"},{"id":"AZL-92217","title":"CVE-2026-59925 affecting package python-mistune for versions less than 3.3.0-1","description":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.","status":"published","published":"2026-07-08T17:17:28Z","modified":"2026-09-09T06:55:05Z","updated_at":"2026-11-02T15:28:11.723718Z"},{"id":"openSUSE-SU-2026:21339-1","title":"Security update for python-mistune","description":"This update for python-mistune fixes the following issues\n\n- CVE-2026-59922: quadratic-time parsing on long runs of some markers in `formatting.py` can lead to DoS (bsc#1271117).\n- CVE-2026-59923: `HTMLRenderer.safe_url()` does not block percent-encoded javascript URIs and allows for XSS\n  (bsc#1271119).\n- CVE-2026-59924: improper processing of user-supplied include paths in `Include.parse()` can lead to path traversal\n  and arbitrary file reads (bsc#1271121).\n- CVE-2026-59925: quadratic-time parsing on long runs of some emphasis pairs in `inline_parser` can lead to DoS\n  (bsc#1271125).\n- CVE-2026-59926: improper escaping in `render_admonition()` can lead to atribute injection and XSS (bsc#1271127).\n- CVE-2026-59927: uncontrolled recursion when processing two markdown files that include each other can lead to a DoS\n   (bsc#1271128).\n- CVE-2026-59928: quadratic-time parsing on long lists of repeated reference-link definitions in `block_parser` can\n  lead to DoS (bsc#1271131).\n- CVE-2026-59929: HARMFUL_PROTOCOLS list misses legacy and chained schemes and allow arbitrary script execution in\n  user agents (bsc#1271132).\n- CVE-2026-59930: the `toc` plugin and `TableOfContents` directive generate heading IDs with predictable values and\n  allow for collisions with attacker-controlled `id=\"toc_N\"` content (bsc#1271082).\n","status":"published","published":"2026-07-14T10:41:18Z","modified":"2026-07-15T10:00:11.548963212Z","updated_at":"2026-11-02T16:58:41.885092Z"},{"id":"SUSE-SU-2026:22655-1","title":"Security update for python-mistune","description":"This update for python-mistune fixes the following issues\n\n- CVE-2026-59922: quadratic-time parsing on long runs of some markers in `formatting.py` can lead to DoS (bsc#1271117).\n- CVE-2026-59923: `HTMLRenderer.safe_url()` does not block percent-encoded javascript URIs and allows for XSS\n  (bsc#1271119).\n- CVE-2026-59924: improper processing of user-supplied include paths in `Include.parse()` can lead to path traversal\n  and arbitrary file reads (bsc#1271121).\n- CVE-2026-59925: quadratic-time parsing on long runs of some emphasis pairs in `inline_parser` can lead to DoS\n  (bsc#1271125).\n- CVE-2026-59926: improper escaping in `render_admonition()` can lead to atribute injection and XSS (bsc#1271127).\n- CVE-2026-59927: uncontrolled recursion when processing two markdown files that include each other can lead to a DoS\n   (bsc#1271128).\n- CVE-2026-59928: quadratic-time parsing on long lists of repeated reference-link definitions in `block_parser` can\n  lead to DoS (bsc#1271131).\n- CVE-2026-59929: HARMFUL_PROTOCOLS list misses legacy and chained schemes and allow arbitrary script execution in\n  user agents (bsc#1271132).\n- CVE-2026-59930: the `toc` plugin and `TableOfContents` directive generate heading IDs with predictable values and\n  allow for collisions with attacker-controlled `id=\"toc_N\"` content (bsc#1271082).\n","status":"published","published":"2026-07-14T10:37:38Z","modified":"2026-07-17T18:24:05.645518218Z","updated_at":"2026-11-02T15:54:03.080707Z"}]}}