# CVE-2026-57076: YAML::Syck heap use-after-free in anchor key handling

Source: https://junglewise.ai/threats/cve-2026-57076-yaml-syck-heap-use-after-free-in-anchor-key-handling  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-16. Updated: 2026-07-16  
License: CC BY 4.0 with a link back

CVE-2026-57076 · Severity: info · CVSS 5.3 · Published 2026-07-16

YAML::Syck is a Perl library used to process YAML data, a common format for configuration files and data exchange. A flaw in how it handles 'anchors' (a way to label and reuse data within a document) allows a specially crafted file to cause the library to read memory that has already been freed. This could potentially lead to information disclosure or application instability when processing untrusted data.

## Quick answers

**Is CVE-2026-57076 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-57076 being exploited in the wild.

**How severe is CVE-2026-57076?** Informational severity, with a CVSS score of 5.3, published 16 July 2026.

**Which products and versions are affected?** TODDR (CPAN) YAML::Syck < 1.47.

**Is there a fix for CVE-2026-57076?** A patch was published on 2026-07-13: Fix committed to repository Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-57076 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-57076?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap use-after-free vulnerability exists in the bundled libsyck library within YAML::Syck. The root cause is improper memory management in 'handler.c' where an anchor name string is shared between a node object and the parser's internal anchors table. When a node is freed, its associated anchor string is also deallocated, but a pointer to that memory remains in the anchors table. If a subsequent anchor redefinition occurs, the parser attempts to compare the new anchor against the freed memory using 'st_strcmp'. This is reachable via the default 'Load' or 'LoadFile' paths when processing untrusted YAML documents. The issue was fixed in version 1.47 by ensuring the anchors table maintains its own private copy of key strings.

## Affected products

- TODDR (CPAN) YAML::Syck < 1.47

## Timeline

- 2026-07-13: patched: Fix committed to repository
- 2026-07-16: disclosed: CVE published via CPANSec and NVD

## References

- [https://cpan.org/modules](https://cpan.org/modules)
- [https://github.com/toddr/YAML-Syck/commit/44c90a109ec3215ee7ce747bd11209835e123d8b.patch](https://github.com/toddr/YAML-Syck/commit/44c90a109ec3215ee7ce747bd11209835e123d8b.patch)
- [https://metacpan.org/release/TODDR/YAML-Syck-1.47/changes](https://metacpan.org/release/TODDR/YAML-Syck-1.47/changes)