Vulnerability in Kagi Fastfeedparser
CVE-2026-39376
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (40.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Kagi Fastfeedparser
- Kagisearch Fastfeedparser — versions < 0.5.10
Weakness classification (CWE)
Public proof-of-concept exploits
References
- github.com/kagisearch/fastfeedparser/security/advisories/GHSA-4gx2-pc4f-wq37 (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-39376?
- CVE-2026-39376 is a high-severity vulnerability in Kagi Fastfeedparser, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2026-04-07.
- How severe is CVE-2026-39376?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2026-39376 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.