What is CVE-2026-26209?

CVE-2026-26209 is a high-severity vulnerability in Agronholm Cbor2, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2026-03-23.

How severe is CVE-2026-26209?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Agronholm Cbor2

CVE-2026-26209

cbor2 provides encoding and decoding for the Concise Binary Object Representation (CBOR) serialization format. Versions prior to 5.9.0 are vulnerable to a Denial of Service (DoS) attack caused by uncontrolled recursion when decoding deeply…

EPSS: 0.001 (24.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Agronholm Cbor2 — versions < 5.9.0

Weakness classification (CWE)

CWE-674 — Uncontrolled Recursion

References

https://github.com/agronholm/cbor2/security/advisories/GHSA-3c37-wwvx-h642 (x_refsource_CONFIRM)
https://github.com/agronholm/cbor2/pull/275 (x_refsource_MISC)
https://github.com/agronholm/cbor2/commit/e61a5f365ba610d5907a0ae1bc72769bba34294b (x_refsource_MISC)
https://github.com/agronholm/cbor2/releases/tag/5.9.0 (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-26209?: CVE-2026-26209 is a high-severity vulnerability in Agronholm Cbor2, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2026-03-23.
How severe is CVE-2026-26209?: High severity. CVSS v3 base score is 7.5 out of 10.