CVE-2026-27171Public exploit

Denial of service via negative CRC length

Published Feb 18, 2026 · Updated Feb 18, 2026

Infinite-loop resource consumption in Ruby zlib before 1.3.2 allows local users to cause a denial of service through CRC combination APIs. The x2nmodp helper repeatedly right-shifts a negative len2 value supplied to crc32_combine64 or crc32_combine_gen64 without reaching its loop terminator. A caller must pass a negative length; the affected process then consumes CPU until interrupted, without reported data disclosure or modification.

CVSS severity2.9
Low
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Infinite-loop resource consumption in Ruby zlib before 1.3.2 allows local users to cause a denial of service through CRC combination APIs. The x2nmodp helper repeatedly right-shifts a negative len2 value supplied to crc32_combine64 or crc32_combine_gen64 without reaching its loop terminator. A caller must pass a negative length; the affected process then consumes CPU until interrupted, without reported data disclosure or modification.

The record

CVE
CVE-2026-27171
Published
Feb 18, 2026
Updated
Feb 18, 2026
Vendor
libwww-perl
Product
zlib
Classifications
CWE-1284, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 18, 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 <1.3.2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

libwww-perl · zlibversion=0 <1.3.2

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
2.9MITRECVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1284Improper Validation of Specified Quantity in Input
T1499.004Application or System Exploitation

Public exploit references

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Technologies

Your stack

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Your stack

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