# CVE-2026-4177: Memory corruption in YAML::Syck

> Heap buffer overflow and memory corruption in YAML::Syck allow attackers to execute code or cause denial of service via crafted YAML input.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Mar 2026
- **Updated:** 15 Jul 2026
- **Also known as:** ALPINE-CVE-2026-4177, ALSA-2026:6470, AZL-109508, AZL-79977, BELL-CVE-2026-4177, DEBIAN-CVE-2026-4177, DSA-6175-1, GHSA-72r6-p2x3-g9gj, MGASA-2026-0058, RHSA-2026:6470, RHSA-2026:8311, RLSA-2026:6470, UBUNTU-CVE-2026-4177, openSUSE-SU-2026:10551-1

## What is CVE-2026-4177?

CVE-2026-4177 is a critical memory corruption vulnerability in TODDR YAML::Syck, published on 16 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter.

The heap overflow occurs when class names exceed the initial 512-byte allocation.

The base64 decoder could read past the buffer end on trailing newlines.

strtok mutated n->type_id in place, corrupting shared node data.

A memory leak occurred in syck_hdlr_add_anchor when a node already had an anchor. The incoming anchor string 'a' was leaked on early return.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input), CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-4177?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `perl-YAML-Syck` | AlmaLinux:8 | All versions | 1.30-6.el8_10 |
| `perl-YAML-Syck` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.30-6.el8_10 |
| `perl-YAML-Syck-debuginfo` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.30-6.el8_10 |
| `perl-YAML-Syck-debugsource` | Red Hat:enterprise_linux:8::crb | All versions | 0:1.30-6.el8_10 |
| `perl-YAML-Syck` | Red Hat:rhel_els:7 | All versions | 0:1.27-3.el7_9.1 |
| `perl-YAML-Syck-debuginfo` | Red Hat:rhel_els:7 | All versions | 0:1.27-3.el7_9.1 |
| `perl-YAML-Syck` | Rocky Linux:8 | All versions | 0:1.30-6.el8_10 |
| `perl-YAML-Syck` | openSUSE:Tumbleweed | All versions | 1.440.0-1.1 |

Products: Toddr Yaml\.

## How do I fix CVE-2026-4177?

Upgrade to a fixed version.

## Is CVE-2026-4177 being exploited?

There is no known exploitation of CVE-2026-4177 in the wild and no public exploit code.

## Other vulnerabilities in TODDR YAML::Syck

- [CVE-2025-11683](https://insights.sbomify.com/CVE-2025-11683/): Information disclosure in YAML::Syck (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4177 and fix it if it is affected.

What it is: CVE-2026-4177 is a critical memory corruption vulnerability in TODDR YAML::Syck, published on 16 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-4177 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-2026-4177/ (Markdown: https://insights.sbomify.com/CVE-2026-4177/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4177
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4177
- OSV: https://osv.dev/vulnerability/CVE-2026-4177

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4177/
Summaries are generated and may contain mistakes; the official description above is the record.