CPANSA-YAML-Syck-2026-57076: YAML-Syck vulnerability
| Publisher | giterlizzi | Document category | csaf_security_advisory |
|---|---|---|---|
| Initial release date | 2026-07-16T00:00:00 | Engine | CSAF Perl Toolkit 0.26 |
| Current release date | 2026-07-16T00:00:00 | Build Date | |
| Current version | 1 | Status | final |
| CVSS v3.1 Base Score | 7.8 | Severity | |
| Original language | Language | en | |
| Also referred to | |||
Vulnerability Description
YAML::Syck versions before 1.47 for Perl allow a heap use-after-free via an anchor name reused as an anchors-table key in syck_hdlr_add_anchor. In the bundled libsyck an anchor name allocated by syck_strndup is stored both as node->anchor, freed when the node is freed, and as the key in the parser's anchors table. Freeing the node frees the shared key, and a later anchor redefinition makes st_delete compare against the freed key, so st_strcmp reads freed heap memory. Anchors are a standard YAML feature and need no special flags, so this is reached on the default Load path. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor reaches the read of freed memory.
Vulnerabilities
CVE-2026-57076
Vulnerability DescriptionYAML::Syck versions before 1.47 for Perl allow a heap use-after-free via an anchor name reused as an anchors-table key in syck_hdlr_add_anchor.
In the bundled libsyck an anchor name allocated by syck_strndup is stored both as node->anchor, freed when the node is freed, and as the key in the parser's anchors table. Freeing the node frees the shared key, and a later anchor redefinition makes st_delete compare against the freed key, so st_strcmp reads freed heap memory. Anchors are a standard YAML feature and need no special flags, so this is reached on the default Load path.
Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor reaches the read of freed memory.
| Weakness | CWE-416 : Use After Free |
|---|
Product status
Known affected
| Product | Score | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| YAML-Syck less than 1.47 |
|
Fixed
- YAML-Syck greater than or equal 1.47
giterlizzi
Namespace: https://github.com/giterlizzi/
gdt@cpan.org
References
- CPANSA-YAML-Syck-2026-57076 JSON self
https://raw.githubusercontent.com/giterlizzi/perl-CPANSA-CSAF/develop/csaf/white/2026/cpansa-yaml-syck-2026-57076.json - https://github.com/toddr/YAML-Syck/commit/44c90a109ec3215ee7ce747bd11209835e123d8b.patch external
https://github.com/toddr/YAML-Syck/commit/44c90a109ec3215ee7ce747bd11209835e123d8b.patch - https://metacpan.org/release/TODDR/YAML-Syck-1.47/changes external
https://metacpan.org/release/TODDR/YAML-Syck-1.47/changes - CVE-2026-57076 (NVD) external
https://nvd.nist.gov/vuln/detail/CVE-2026-57076
Revision history
| Version | Date of the revision | Summary of the revision |
|---|---|---|
| 1 | Thu Jul 16 00:00:00 2026 | First release |
Sharing rules
TLP:WHITE
For the TLP version see: https://www.first.org/tlp/