CVE-2026-4176: Perl versions from 5.9.4 before 5.40.4-RC1, from 5.41.0 before 5.42.2-RC1, from 5.43.0 before 5.43.9 contain a

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CRITICAL 9.8REMOTEUPGRADE

CVE-2026-4176 is a critical-severity flaw (CVSS 9.8) affecting perl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Perl versions from 5.9.4 before 5.40.4-RC1, from 5.41.0 before 5.42.2-RC1, from 5.43.0 before 5.43.9 contain a vulnerable version of Compress::Raw::Zlib. Compress::Raw::Zlib is included in the Perl package as a dual-life core module, and is vulnerable to CVE-2026-3381 due to a vendored version of zlib which has several vulnerabilities, including CVE-2026-27171. The bundled Compress::Raw::Zlib was updated to version 2.221 in Perl blead commit c75

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.7% (top 46%)
CISA exploited list	No
Published	2026-03-29
Last modified	2026-06-17

Publisher (CNA): CPANSec · Vendor: perl

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-29 21:16 UTCPublished CVE record published
2026-06-17 10:56 UTCUpdated Record last modified

perl perl UPGRADE

Affected: >= 5.9.4 and < 5.40.4 · >= 5.41.0 and < 5.42.2 · >= 5.43.0 and < 5.43.9

Fixed in: 5.40.4, 5.42.2, 5.43.9

Safe to downgrade to: a release before 5.9.4

1. Check installed version

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

2. UPGRADE to 5.40.4 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade perl

Note

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

3. If no update is available yet, DOWNGRADE to a release before 5.9.4 (Debian / Ubuntu)

apt-cache madison perl sudo apt install perl=<VERSION_BEFORE_5.9.4> sudo apt-mark hold perl

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list perl sudo dnf downgrade perl-<VERSION_BEFORE_5.9.4> sudo dnf versionlock add perl

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2026-4176?

perl: upgrade to 5.40.4, 5.42.2, 5.43.9. Exact commands for each OS are on this page.

Is CVE-2026-4176 being exploited?

CVE-2026-4176 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-2026-4176 affect?

CVE-2026-4176 affects perl. Severity is critical (CVSS 9.8). Perl versions from 5.9.4 before 5.40.4-RC1, from 5.41.0 before 5.42.2-RC1, from 5.43.0 before 5.43.9 contain a vulnerable version of Compress::Raw::Zlib. Compress::Raw::Zlib is included in the Perl package as a dual-life core module, and i

How urgent is CVE-2026-4176?

Priority 53/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Perl vulnerabilities · zlib vulnerabilities

Related CVEs

CVE-2026-13221 CRITICAL 9.1 UPGRADE Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.10 produce silently in
CVE-2026-57432 HIGH 8.4 UPGRADE Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.11 have an integer ove
CVE-2026-8376 CRITICAL 9.8 UPGRADE Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.11 have a heap buffer

References

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