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PerlApplication

CVE-2026-4176

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-29
Fix available
A fix is available. Upgrade to 5.40.4 / 5.42.2 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 c75ae9cc164205e1b6d6dbd57bd2c65c8593fe94.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Perl versions 5.9.4 through 5.40.4-RC1, 5.41.0 through 5.42.2-RC1, and 5.43.0 through 5.43.9 include a vulnerable bundled version of Compress::Raw::Zlib (up to 2.221) which contains a vendored copy of zlib with multiple vulnerabilities including CVE-2026-3381 and CVE-2026-27171, allowing potential remote code execution or denial of service via crafted compressed data.

MitigationUpgrade Perl to version 5.40.4-RC1/5.42.2-RC1/5.43.9 or later stable releases which include Compress::Raw::Zlib 2.221 with the patched zlib library.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
PerlApplication
Affected:>= 5.9.4, < 5.40.4>= 5.41.0, < 5.42.2>= 5.43.0, < 5.43.9

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed Perl version
    Run `perl -v` or `perl --version` to display the Perl interpreter version
    Affected if Perl version is >= 5.9.4 and < 5.40.4, OR >= 5.41.0 and < 5.42.2, OR >= 5.43.0 and < 5.43.9
  2. Identify Compress::Raw::Zlib version
    Run `perl -MCompress::Raw::Zlib -e 'print $Compress::Raw::Zlib::VERSION'` to print the module version
    Affected if Compress::Raw::Zlib version is 2.221 or earlier (the vulnerable bundled version)
  3. Verify zlib vendoring in Perl
    Check the Perl installation for a vendored zlib library within the Compress::Raw::Zlib or Perl lib paths
    Affected if A vendored copy of zlib exists in the Perl distribution (indicating the bundled vulnerable library is in use)
  4. Audit code for Compress::Raw::Zlib usage
    Search codebase for `use Compress::Raw::Zlib` or `require Compress::Raw::Zlib` statements, and review any inflateInit/new/DESTROY calls
    Affected if The application uses Compress::Raw::Zlib to process compressed data, particularly from untrusted sources

You are affected if your Perl version falls within the vulnerable ranges AND your code uses Compress::Raw::Zlib to decompress data, especially from untrusted or external sources.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.40.4 / 5.42.2 / 5.43.9 or later
Fixed in 5.40.45.42.25.43.9
Vendor patch github.com →
Interim mitigation

Upgrade Perl to version 5.40.4-RC1/5.42.2-RC1/5.43.9 or later stable releases which include Compress::Raw::Zlib 2.221 with the patched zlib library.

Recommended fix High confidence

Perl 5.40.4+ (stable), 5.42.2+ (stable), or 5.43.9+ (development) depending on your release track

  1. Check current Perl version with: perl -v
  2. Determine your release track (5.40.x, 5.42.x, or 5.43.x) and upgrade to the corresponding fixed version
  3. For Perl 5.40.x: upgrade to 5.40.4 or later
  4. For Perl 5.41.x: upgrade to 5.42.2 or later
  5. For Perl 5.43.x: upgrade to 5.43.9 or later
  6. Verify Compress::Raw::Zlib version is 2.221 or later: perl -MCompress::Raw::Zlib -e 'print $Compress::Raw::Zlib::VERSION'
Caveat Major Perl version upgrades may introduce backward incompatibilities; test thoroughly before production deployment

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Perl Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing12.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,760
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,616.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-4176 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data