CVE-2026-39376 — HIGH (7.5)

Vulnerability 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.

CVSS Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

NONE

Availability

HIGH

Affected Products

Vendor	Product	Versions
Kagi	Fastfeedparser	< 0.5.10

Related Weaknesses (CWE)

CWE-674

References

https://github.com/kagisearch/fastfeedparser/security/advisories/GHSA-4gx2-pc4f-ExploitVendor Advisory
https://github.com/kagisearch/fastfeedparser/security/advisories/GHSA-4gx2-pc4f-ExploitVendor Advisory

FAQ

What is CVE-2026-39376?

CVE-2026-39376 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 ...

How severe is CVE-2026-39376?

CVE-2026-39376 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-39376?

Check the references section above for vendor advisories and patch information. Affected products include: Kagi Fastfeedparser.