CVE-2026-13713 Use after free in YAML::Syck
Attackers can crash the Perl interpreter by supplying a crafted YAML document that triggers a use-after-free and double-free in the YAML::Syck library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-13713?
CVE-2026-13713 is a medium-severity use after free vulnerability in TODDR YAML::Syck, published on 16 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-13713?
Linux distribution packages (5)
perl-YAML-Syck AlmaLinux:8 | All versions | 1.30-7.el8_10 |
perl-YAML-Syck Red Hat:enterprise_linux:8::crb | All versions | 0:1.30-7.el8_10 |
perl-YAML-Syck-debuginfo Red Hat:enterprise_linux:8::crb | All versions | 0:1.30-7.el8_10 |
perl-YAML-Syck-debugsource Red Hat:enterprise_linux:8::crb | All versions | 0:1.30-7.el8_10 |
perl-YAML-Syck Rocky Linux:8 | All versions | 0:1.30-7.el8_10 |
How do I fix CVE-2026-13713?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-13713 being exploited?
There is no known exploitation of CVE-2026-13713 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-13713, ALSA-2026:67269, AZL-109520, AZL-92904, BELL-CVE-2026-13713, DEBIAN-CVE-2026-13713 and 4 more.