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Vulnerability record · CVE-2026-39376 · published 7 April 2026

CVE-2026-39376: Kagi fastfeedparser vulnerability

Kagi · Fastfeedparser

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.

7.5 CVSS 3.1 High EPSS 0.50% · top 59.8% CWE-674 · CWE-674
7.5CVSS 3.1 base score
0.50%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
24 Jul 2026Last modified by NVD

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/kagisearch/fastfeedparser/security/advisories/GHSA-4gx2-pc4f-wq37 ExploitVendor Advisory
https://github.com/kagisearch/fastfeedparser/security/advisories/GHSA-4gx2-pc4f-wq37 ExploitVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2026-39376), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.