CVE-2025-40927Network attack vector

Response splitting via incomplete newline validation

Published Aug 29, 2025 · Updated Aug 29, 2025

HTTP response splitting in CGI::Simple before 1.282 allows remote attackers to inject response headers through crafted query parameters. The header() routine checked only its configured CRLF sequence, so URL-decoded lone LF or CR characters in query-derived values reached generated headers. An affected CGI application must pass attacker-controlled parameters into header generation; the injected response can enable reflected XSS, redirects, cache poisoning, or header manipulation.

CVSS severityUnavailable
Unscored
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP response splitting in CGI::Simple before 1.282 allows remote attackers to inject response headers through crafted query parameters. The header() routine checked only its configured CRLF sequence, so URL-decoded lone LF or CR characters in query-derived values reached generated headers. An affected CGI application must pass attacker-controlled parameters into header generation; the injected response can enable reflected XSS, redirects, cache poisoning, or header manipulation.

The record

CVE
CVE-2025-40927
Published
Aug 29, 2025
Updated
Aug 29, 2025
Vendor
Mohammad Sajid Anwar
Product
CGI::Simple
Classifications
CWE-113
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 29, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 29, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=0 <1.282

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mohammad Sajid Anwar · CGI::Simpleversion=0 <1.282

Published CVSS scores

No CVSS assessment is available in this record.

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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