CVE-2026-4177
YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-severity heap buffer overflow in the YAML emitter
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.
INFO
Published Date :
March 16, 2026, 11:16 p.m.
Last Modified :
March 23, 2026, 6:17 p.m.
Remotely Exploit :
Yes !
Source :
9b29abf9-4ab0-4765-b253-1875cd9b441e
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
Solution
- Update YAML::Syck to a fixed version.
- Ensure the emitter handles class names correctly.
- Validate base64 decoding logic.
- Check strtok function for data corruption.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-4177.
| URL | Resource |
|---|---|
| https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch | Patch |
| https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21 | Release Notes |
| http://www.openwall.com/lists/oss-security/2026/03/16/6 | Mailing List Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-4177 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-4177
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-4177 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-4177 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Mar. 23, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:toddr:yaml::syck:*:*:*:*:*:perl:*:* versions up to (excluding) 1.37 Added Reference Type CVE: http://www.openwall.com/lists/oss-security/2026/03/16/6 Types: Mailing List, Third Party Advisory Added Reference Type CPANSec: https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch Types: Patch Added Reference Type CPANSec: https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21 Types: Release Notes -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Mar. 17, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Mar. 17, 2026
Action Type Old Value New Value Added Reference http://www.openwall.com/lists/oss-security/2026/03/16/6 -
New CVE Received by 9b29abf9-4ab0-4765-b253-1875cd9b441e
Mar. 16, 2026
Action Type Old Value New Value Added 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. Added CWE CWE-122 Added Reference https://github.com/cpan-authors/YAML-Syck/commit/e8844a31c8cf0052914b198fc784ed4e6b8ae69e.patch Added Reference https://metacpan.org/release/TODDR/YAML-Syck-1.37_01/changes#L21