CVE-2026-120639VulnerabilityPublished 4 Nov 2026Updated 12 Nov 2026

Libcgi pm perl: CGI versions before 5.00 for Perl allow HTTP header injection via entity decoding after the newline

Affects libcgi-pm-perlSource GCVE Database

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Authoritative record:CVE-2026-120639· High 7.2

Not known to be exploited · CVSS 7.2 High.

Data as of 12 Nov 2026, 22:05 UTC

CVSS 3.1 base score

7.2High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CISA-ADP	CVSS 3.1	7.2

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 12 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.10libcgi-pm-perl`pkg:deb/ubuntu/libcgi-pm-perl?arch=source&distro=stonking`Other threats	Affected =4.71-1build1 =4.72-1	Fixed in–
Ubuntu 26.04 LTSlibcgi-pm-perl`pkg:deb/ubuntu/libcgi-pm-perl?arch=source&distro=resolute`Other threats	Affected =4.68-1 =4.71-1 =4.71-1build1	Fixed in–
Ubuntu 24.04 LTSlibcgi-pm-perl`pkg:deb/ubuntu/libcgi-pm-perl?arch=source&distro=noble`Other threats	Affected 4.57-1 – 4.63-1 5 affected builds	Fixed in–
Ubuntu 22.04 LTSlibcgi-pm-perl`pkg:deb/ubuntu/libcgi-pm-perl?arch=source&distro=jammy`Other threats	Affected =4.51-1 =4.53-1 =4.54-1	Fixed in–
Ubuntu 20.04 LTSlibcgi-pm-perl`pkg:deb/ubuntu/libcgi-pm-perl?arch=source&distro=focal`Other threats	Affected =4.44-1 =4.45-1 =4.46-1	Fixed in–
Ubuntu 18.04 LTSlibcgi-pm-perl`pkg:deb/ubuntu/libcgi-pm-perl?arch=source&distro=bionic`Other threats	Affected =4.36-1 =4.37-1 =4.38-1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until a fix is available, avoid passing untrusted user input directly into HTTP header values processed by libcgi-pm-perl. Consider applying input validation or escaping to prevent injection of newline characters.

Description

Libcgi pm perl versions before 5.00 contain a vulnerability that allows HTTP header injection via improper entity decoding after newline checks and unchecked header values in multipart processing functions. This can enable an attacker to inject headers or split HTTP responses when user input is passed into these header values.

Impact

Successful exploitation can lead to HTTP header injection, which may allow attackers to add arbitrary headers or split HTTP responses. This can facilitate attacks such as HTTP response splitting, cache poisoning, or cross-site scripting (XSS) in some contexts. The CVSS score of 7.2 (high) reflects the network attack vector with low complexity and no privileges or user interaction required, impacting confidentiality and integrity with no availability impact.

Summary

The vulnerability exists in libcgi-pm-perl versions prior to 5.00, where the HTTP header processing improperly decodes HTML entities after checking for newlines, allowing encoded carriage return (CR) or line feed (LF) characters to reach the response. Additionally, the multipart_start function does not validate header values for newlines, and the do_push function does not verify the type of data it outputs in each multipart section. These flaws combined permit an attacker to inject additional HTTP headers or manipulate the response structure if the application uses untrusted request data in these header values.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2026, 22:05 UTC

Technical details

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