# 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.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 16 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** ALPINE-CVE-2026-57076, AZL-109502, AZL-92910, BELL-CVE-2026-57076, DEBIAN-CVE-2026-57076, GHSA-q6x2-vfpr-9j7p, UBUNTU-CVE-2026-57076

## 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 (Use After Free)

## Which versions are affected by CVE-2026-57076?


## How do I fix CVE-2026-57076?

Upgrade to a fixed version.

## Is CVE-2026-57076 being exploited?

There is no known exploitation of CVE-2026-57076 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57076 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-57076 in the wild and no public exploit code.

Affected product: TODDR YAML::Syck. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-57076/ (Markdown: https://insights.sbomify.com/CVE-2026-57076/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57076
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57076
- OSV: https://osv.dev/vulnerability/CVE-2026-57076

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-57076/
Summaries are generated and may contain mistakes; the official description above is the record.