Process crash via unbounded meta-refresh recursion
Published Apr 7, 2026 · Updated Apr 7, 2026
Uncontrolled recursion in FastFeedParser before 0.5.10 allows remote attackers to crash a consuming process via HTML meta-refresh chains. In parse(), an XML parsing failure triggers _extract_meta_refresh_url(), then the returned URL is fetched through an unconditional recursive call without a depth, visit, or redirect limit. Exposure requires a consuming application to pass an attacker-controlled feed URL; a looping server can hold a worker until Python raises RecursionError and crashes that process.
Summary
What happened
Uncontrolled recursion in FastFeedParser before 0.5.10 allows remote attackers to crash a consuming process via HTML meta-refresh chains. In parse(), an XML parsing failure triggers _extract_meta_refresh_url(), then the returned URL is fetched through an unconditional recursive call without a depth, visit, or redirect limit. Exposure requires a consuming application to pass an attacker-controlled feed URL; a looping server can hold a worker until Python raises RecursionError and crashes that process.
The record
- CVE
- CVE-2026-39376
- Published
- Apr 7, 2026
- Updated
- Apr 7, 2026
- Vendor
- Kagi
- Product
- FastFeedParser
- Classifications
- CWE-674, CWE-400, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 7, 2026CVE publishedPublication date reported by the CVE source.
- Apr 7, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 0.5.10
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-4gx2-pc4f-wq37 embedded proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo