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Vulnerability · Published Sep 24, 2026 · Assigned by mitre

CVE-2026-88359

Medium 6.5

In plain English

A medium-severity resource allocation without limits in the libfyaml package (Debian). Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.3%top 77.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

libfyaml 0.9.6 contains a stack exhaustion vulnerability in fy_atom_iter_format(). When processing a specially crafted YAML document containing a very large literal or folded block scalar, the function repeatedly grows an internal buffer using alloca() inside a loop. The allocated stack memory is not released until the function returns, causing cumulative stack growth that can exceed the process stack limit and result in SIGSEGV and denial of service.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12libfyamlno fix listedDEBIAN-CVE-2026-88359
Debian:13libfyamlno fix listedDEBIAN-CVE-2026-88359
Debian:14libfyamlno fix listedDEBIAN-CVE-2026-88359
Ubuntu:22.04:LTSlibfyamlno fix listedUBUNTU-CVE-2026-88359
Ubuntu:24.04:LTSlibfyamlno fix listedUBUNTU-CVE-2026-88359
Ubuntu:26.04:LTSlibfyamlno fix listedUBUNTU-CVE-2026-88359
Ubuntu:26.10libfyamlno fix listedUBUNTU-CVE-2026-88359

Affected products (as reported)

VendorProductVersions
n/a n/a n/a

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

References