Vulnerability · Published Apr 7, 2026 · Assigned by GitHub_M
CVE-2026-39376FastFeedParser has an infinite redirect loop DoS via meta-refresh chain
High 7.5
In plain English
A high-severity security flaw in fastfeedparser from kagisearch. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | fastfeedparser | 0.5.10 | GHSA-4gx2-pc4f-wq37 |
| PyPI | fastfeedparser | 0.5.10 | PYSEC-2026-60 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| kagisearch | fastfeedparser | < 0.5.10 |
Weakness: CWE-674 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H