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Fencer Vulns
high 7.3

CVE-2026-5089 json

YAML::Syck versions before 1.38 for Perl has an out-of-bounds read

published 2026-05-12 5 mo ago modified 2026-10-26 13 d ago also EUVD-2026-29543

cvss
7.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 34%
public exploits
0
none known

Summary

YAML::Syck versions before 1.38 for Perl has an out-of-bounds read.

The base60 (sexagesimal) parsing code in perl_syck.h has a buffer underflow bug in both int#base60 and float#base60 handlers. When processing the leftmost segment of a colon-separated value (e.g., the 1 in 1:30:45), the inner while loop can decrement a pointer past the start of the string buffer:

while ( colon >= ptr && *colon != ':' ) { colon--; } if ( *colon == ':' ) *colon = '\0'; // colon may be ptr-1 here

When no colon is found (final/leftmost segment), colon becomes ptr-1, and the subsequent *colon dereference reads one byte before the allocated buffer.

Patch / fix

  • TODDR YAML::Syck 1.38
  • libyaml-syck-perl Debian 12 1.34-2+deb12u3
  • libyaml-syck-perl Debian 13 1.34-2+deb13u3
  • libyaml-syck-perl Debian 14 1.36-3

debian advisories DEBIAN-CVE-2026-5089

  • perl-YAML-Syck openSUSE Leap 16.0 1.450.0-bp160.2.1
  • perl-YAML-Syck openSUSE Tumbleweed 1.450.0-4.1

opensuse advisories openSUSE-SU-2026:20938-1openSUSE-SU-2026:10846-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-5089 updated cvss 4.0

perl-YAML-Syck: perl-YAML-Syck: Information disclosure via out-of-bounds read in base60 parsing

  • Red Hat Enterprise Linux 6 perl-YAML-Syck Red Hat Enterprise Linux 8 perl-YAML-Syck
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/cpan-authors/YAML-Syck/issues/132 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
CNA 3.1 7.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Affected products

  • TODDR YAML::Syck

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.