CVE-2026-39376
FastFeedParser has an infinite redirect loop DoS via meta-refresh chain
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.
How to fix CVE-2026-39376
To remediate CVE-2026-39376, upgrade the affected package to a fixed version below.
- —upgrade to 0.5.10 or later
- —upgrade to 0.5.10 or later
Is CVE-2026-39376 being exploited?
Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.
Affected packages (2)
- from 0, < 0.5.10
- from 0, < 0.5.10
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |