CairoSVG: Quadratic-time DoS parsing a crafted SVG

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-107378: 0.38% estimated exploitation activity in the next 30 days; percentile 32.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Rendering an untrusted SVG whose <path d="..." contains many segments is O(n²) CPU. A single <path under 1 MiB burns tens of seconds. Two independent O(n²) sites in cairosvg/path.py: 1. Tokenizer — the path-data parser consumes the d string with a while string: loop that repeatedly slices/re-scans the remaining string (each step is O(len remaining)), giving O(n²) over the whole attribute. 2. drawmarkers — marker handling drains node.vertices with while node.vertices: ... node.vertices.pop(0); list.pop(0) is O(n), so draining n vertices is O(n²). Both are hit on a normal render path (svg2png/svg2pdf), attacker controls only the SVG document. PoC (installed cairosvg 2.9.0) | path segments | SVG size | time | |---|---|---| | 50,000 | 244 KB | 1.14 s | | 100,000 | 488 KB | 4.36 s | | 200,000 | ~960 KB | ~18 s | Doubling segments ≈ 4× time ⇒ quadratic. Sub-MiB input ⇒ ~18 s CPU; any service rendering user-supplied SVG (thumbnails, avatars, PDF export) is a DoS target. Reachability…

Published by the source

8 Oct 2026, 19:41 UTC

Last modified by the source

15 Oct 2026, 14:56 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-c3jg-qh8m-j3h2

2. Revision 3 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-c3jg-qh8m-j3h2

4. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-c3jg-qh8m-j3h2

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# Patch Next advisory brief: CVE-2026-107378

Advisory: CairoSVG: Quadratic-time DoS parsing a crafted SVG
IDs: CVE-2026-107378, GHSA-c3jg-qh8m-j3h2
Record: https://patchnext.com/advisories/cve-2026-107378 (revision 4, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: cairosvg 2.9.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI cairosvg: affected <= 2.9.0; fixed in 2.9.1

## Suggested inspection (read-only)
- `python -m pip show cairosvg`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on cairosvg.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c3jg-qh8m-j3h2 (GitHub-reviewed advisory GHSA-c3jg-qh8m-j3h2 lists affected ranges: PyPI cairosvg >=0 <=2.9.0)
- Verified: https://osv.dev/vulnerability/GHSA-c3jg-qh8m-j3h2 (OSV record GHSA-c3jg-qh8m-j3h2 lists affected ranges: PyPI cairosvg >=0 <2.9.1 (fixed))

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