VulnerabilityPublished 4 Nov 2026Updated 12 Nov 2026

CVE-2026-120651: Libcgi pm perl · CGI versions before 5.00 for Perl allow an infinite loop on a short request body

Affects libcgi-pm-perlSource GCVE Database

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Authoritative record:CVE-2026-120651· High 7.5

Not known to be exploited · CVSS 7.5 High.

Data as of 12 Nov 2026, 21:02 UTC

CVSS 3.1 base score

7.5High

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	7.5

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

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

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: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

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, consider disabling or restricting access to vulnerable CGI scripts or applying network-level protections to mitigate potential denial of service attempts.

Description

CGI versions before 5.00 for Perl contain a vulnerability that allows an infinite loop when processing a short request body with $DISABLE_UPLOADS set. This occurs because the code reads until the Content-Length bytes have arrived, but if the body is shorter than declared, the read returns 0 repeatedly, causing the server process to hang indefinitely. This can be exploited by a client to keep a server process spinning, resulting in a denial of service.

Impact

An attacker can send a specially crafted HTTP request with a short request body and a Content-Length header that is longer than the actual body. This causes the server process handling the request to enter an infinite loop, consuming resources and potentially leading to denial of service. The vulnerability does not affect confidentiality or integrity but impacts availability.

Summary

The vulnerability in libcgi-pm-perl versions prior to 5.00 arises when $CGI::DISABLE_UPLOADS is set and a request body shorter than the declared Content-Length is received. The function read_postdata_putdata attempts to discard the body by reading until the specified Content-Length is reached. However, if the actual body is shorter, each read returns 0, causing an infinite loop that prevents the server process from terminating. This can be exploited by an attacker to cause a denial of service by tying up server resources indefinitely.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2026, 21:02 UTC

Technical details

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