# 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.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **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-2026-13713, ALSA-2026:67269, AZL-109520, AZL-92904, BELL-CVE-2026-13713, DEBIAN-CVE-2026-13713, GHSA-p3p9-6pr6-mr9m, RHSA-2026:67269, RLSA-2026:67269, UBUNTU-CVE-2026-13713

## 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.

Weakness: CWE-416 (Use After Free), CWE-415 (Double Free)

## Which versions are affected by CVE-2026-13713?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `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.

## Is CVE-2026-13713 being exploited?

There is no known exploitation of CVE-2026-13713 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-13713 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-13713 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-2026-13713/ (Markdown: https://insights.sbomify.com/CVE-2026-13713/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-13713
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-13713
- OSV: https://osv.dev/vulnerability/CVE-2026-13713

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-13713/
Summaries are generated and may contain mistakes; the official description above is the record.