VulnerabilityPublished 3 Nov 2026

CVE-2026-120643: CGI (Perl module) · Cross-site Scripting

Affects CGI (Perl module)Source CVE Database V5

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Not known to be exploited : upgrade to 5.00 soon.

Data as of 4 Nov 2026, 01:00 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Patch: Available – fixed in 5.00

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 3 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

Upgrade CGI (Perl module) to 5.00.

Affected software

Product	Affected	Fixed in
CGI	Affected >=4.62 <5.00	Fixed in 5.00
CPANCGI`pkg:cpan/CGI`Other threats	Affected >=4.62 <5.00	Fixed in 5.00

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

AI-suggested

Upgrade to CGI version 5.00 or later, where this vulnerability is fixed. No additional mitigation steps are indicated by the vendor advisory.

Description

A cross-site scripting (XSS) vulnerability exists in CGI versions from 4.62 up to but not including 5.00 for Perl. The flaw arises because the URL returned by the url and self_url methods can contain a raw apostrophe due to how URI's canonical method processes it. This raw apostrophe can appear in single-quoted HTML attributes or JavaScript strings, enabling XSS attacks. The issue is fixed in version 5.00.

Impact

This vulnerability allows an attacker to inject malicious scripts into web pages by exploiting unescaped apostrophes in URLs. This can lead to cross-site scripting attacks, potentially compromising user sessions, stealing sensitive information, or performing actions on behalf of the user within the affected application context.

Summary

CGI Perl versions >=4.62 and <5.00 are vulnerable to cross-site scripting via a raw apostrophe in URLs returned by the url and self_url methods. These methods pass the URL through URI's canonical method, which leaves apostrophes raw in the path and decodes %27 in query parameters, resulting in unescaped apostrophes in the output. If an application embeds these URLs within single-quoted HTML attributes or JavaScript strings, it can lead to XSS exploitation. The vulnerability is addressed in CGI version 5.00.

CWE-79Improper Neutralization of Input During Web Page Generation (Cross-site Scripting) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2026, 01:00 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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