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CVE-2026-39376

Kagi Fastfeedparser denial of service

7.5 HIGHPublic exploitEPSS 0.50%
  1. Published7 Apr 2026

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 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Kagi Fastfeedparser< 0.5.10

Remediation

Fixed in
Kagi Fastfeedparser≥ 0.5.10

References

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Frequently asked

Is CVE-2026-39376 being actively exploited?

CVE-2026-39376 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.50%.

How severe is CVE-2026-39376?

CVE-2026-39376 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.50% probability of exploitation.

Which products are affected by CVE-2026-39376?

Affected products include Kagi Fastfeedparser.

How do I fix CVE-2026-39376?

Upgrade affected software to a fixed version, for example Kagi Fastfeedparser 0.5.10 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-39376 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.