CVE-2026-4177: YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter

[Timothy Legge <timlegge () cpansec org>]

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CVE-2026-4177                                        CPAN Security Group
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        CVE ID:  CVE-2026-4177
  Distribution:  YAML-Syck
      Versions:  through 1.36

      MetaCPAN:  https://metacpan.org/dist/YAML-Syck
      VCS Repo:  https://github.com/cpan-authors/YAML-Syck


YAML::Syck versions through 1.36 for Perl has several potential
security vulnerabilities including a high-severity heap buffer overflow
in the YAML emitter

Description
-----------
YAML::Syck versions through 1.36 for Perl has several potential
security vulnerabilities including a high-severity heap buffer overflow
in the YAML emitter.

The heap overflow occurs when class names exceed the initial 512-byte
allocation.

The base64 decoder could read past the buffer end on trailing newlines.

strtok mutated n->type_id in place, corrupting shared node data.

A memory leak occurred in syck_hdlr_add_anchor when a node already had
an anchor. The incoming anchor string 'a' was leaked on early return.

Problem types
-------------
- CWE-122 Heap-based Buffer Overflow

Solutions
---------
Upgrade to version 1.37 or higher when it is available.


References
----------
https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch
https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21

Credits
-------
Todd Rinaldo, finder