CVE-2026-3381Public exploitNetwork attack vector

CPU exhaustion via nonterminating CRC shift loop

Published Mar 5, 2026 · Updated Mar 5, 2026

Denial of service in Compress::Raw::Zlib 2.219 and earlier allows remote attackers to consume CPU via crafted CRC-combination lengths. Its bundled zlib passes a negative length into x2nmodp, whose right-shift loop never terminates through crc32_combine64 or crc32_combine_gen64. Reachability depends on a consuming Perl application exposing either CRC-combination API to attacker-controlled lengths; exploitation hangs the calling process rather than altering or disclosing data.

CVSS severity9.8
Critical
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Compress::Raw::Zlib 2.219 and earlier allows remote attackers to consume CPU via crafted CRC-combination lengths. Its bundled zlib passes a negative length into x2nmodp, whose right-shift loop never terminates through crc32_combine64 or crc32_combine_gen64. Reachability depends on a consuming Perl application exposing either CRC-combination API to attacker-controlled lengths; exploitation hangs the calling process rather than altering or disclosing data.

The record

CVE
CVE-2026-3381
Published
Mar 5, 2026
Updated
Mar 5, 2026
Vendor
Paul Marquess
Product
Compress::Raw::Zlib
Classifications
CWE-1395, CWE-1284, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=2.219

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Paul Marquess · Compress::Raw::Zlibversion=0 <=2.219

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1395Dependency on Vulnerable Third-Party Component
CWE-1284Improper Validation of Specified Quantity in Input
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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