VulnerabilityDeferred

CVE-2026-13713

YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack.

MEDIUM 6.2EPSS 0.13%

Does this matter?

Lower severity and a low EPSS score (0.13%). Track it; it rarely justifies an emergency change on its own.

Description

YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack. In the bundled libsyck, when an anchor name is redefined or removed, syck_hdlr_add_anchor and syck_hdlr_remove_anchor free the node stored under that name with syck_free_node. That node can still be live on the parser's value stack, so syck_hdlr_add_node reaches it again and frees it a second time. On a normal build the 48-byte node chunk is freed twice and the interpreter aborts. Anchors need no special flags, so this is reached on the default Load path, and a 7-byte document that redefines an anchor triggers it. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor mid-parse crashes the interpreter, a denial of service.

CVSS 3.1: 6.2 MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.13% probability · 3th percentile
CISA KEV: Not listed
Weakness: CWE-415, CWE-416
Source: 9b29abf9-4ab0-4765-b253-1875cd9b441e

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.