CVE-2026-4177

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, service disruption.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-03-16 23:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-07-15 02:22 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 9.1 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-03-16 23:16 UTC

Last modified

2026-07-15 02:22 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-122

Record status

Modified

Affected

• Toddr yaml\ < 1.37

Attack profile CVSS 3.1 · 9.1

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-4177.md and follow it. Check whether this project is affected by CVE-2026-4177. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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