CVE-2026-4177: YAML::Syck versions through 1.36 for Perl has several potential security vulnerabilities including a high-seve

Q: How do I fix CVE-2026-4177?

yaml\: upgrade to 1.37. Exact commands for each OS are on this page.

Q: Is CVE-2026-4177 being exploited?

CVE-2026-4177 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-4177 affect?

CVE-2026-4177 affects yaml\. Severity is critical (CVSS 9.1). 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.

Q: How urgent is CVE-2026-4177?

Priority 47/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2026-4177 is a critical-severity flaw (CVSS 9.1) affecting yaml\. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 61%)
CISA exploited list	No
Weakness	CWE-122, CWE-120
Published	2026-03-16
Last modified	2026-07-15

Publisher (CNA): CPANSec · Vendor: toddr

Last updated 2026-07-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-16 23:16 UTCPublished CVE record published
2026-07-15 02:22 UTCUpdated Record last modified

toddr yaml\ UPGRADE

Affected: < 1.37

Fixed in: 1.37

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy yaml || rpm -q yaml || yaml --version

2. UPGRADE to 1.37 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade yaml

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade yaml

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-4177?

yaml\: upgrade to 1.37. Exact commands for each OS are on this page.

Is CVE-2026-4177 being exploited?

CVE-2026-4177 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-4177 affect?

CVE-2026-4177 affects yaml\. Severity is critical (CVSS 9.1). 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.

How urgent is CVE-2026-4177?

Priority 47/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Perl vulnerabilities

Related CVEs

CVE-2025-11683 MEDIUM 6.5 UPGRADE YAML::Syck versions before 1.36 for Perl has missing null-terminators which causes out-of-bounds read and pote

References

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