CVE-2026-57076 Use after free in YAML::Syck
Attackers can trigger a heap use-after-free in YAML::Syck by crafting malicious YAML documents, potentially leading to code execution or crashes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-57076?
CVE-2026-57076 is a high-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 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
Which versions are affected by CVE-2026-57076?
How do I fix CVE-2026-57076?
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-2026-57076 being exploited?
There is no known exploitation of CVE-2026-57076 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-57076, AZL-109502, AZL-92910, BELL-CVE-2026-57076, DEBIAN-CVE-2026-57076, GHSA-q6x2-vfpr-9j7p and 1 more.