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Vulnerability record · CVE-2025-27220 · published 4 March 2025

CVE-2025-27220: Ruby-lang cgi inefficient regular expression (redos) vulnerability

Ruby Lang · Cgi

In the CGI gem before 0.4.2 for Ruby, a Regular Expression Denial of Service (ReDoS) vulnerability exists in the Util#escapeElement method.

7.5 CVSS 3.1 High EPSS 0.76% · top 46.5% CWE-1333 · Inefficient regular expression (ReDoS)
7.5CVSS 3.1 base score
0.76%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
17 Jun 2026Last modified by NVD

Description

In the CGI gem before 0.4.2 for Ruby, a Regular Expression Denial of Service (ReDoS) vulnerability exists in the Util#escapeElement method.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/cgi/CVE-2025-27220.yml Third Party Advisory
https://hackerone.com/reports/2890322 Permissions Required
https://lists.debian.org/debian-lts-announce/2025/03/msg00008.html

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2021-41816Ruby-lang cgi integer overflow vulnerabilityCGI.escape_html in Ruby before 2.7.5 and 3.x before 3.0.3 has an integer overflow and resultant buffer overflow via a long string on platforms (such …EPSS 4.8%8.8CVE-2021-33621Ruby-lang cgi injection vulnerabilityThe cgi gem before 0.1.0.2, 0.2.x before 0.2.2, and 0.3.x before 0.3.5 for Ruby allows HTTP response splitting. This is relevant to applications that…EPSS 2.4%7.5CVE-2025-27219Ruby-lang cgi allocation without limits vulnerabilityIn the CGI gem before 0.4.2 for Ruby, the CGI::Cookie.parse method in the CGI library contains a potential Denial of Service (DoS) vulnerability. The…EPSS 0.85%7.5CVE-2021-41819Ruby-lang cgi reliance on cookies without validation vulnerabilityCGI::Cookie.parse in Ruby through 2.6.8 mishandles security prefixes in cookie names. This also affects the CGI gem through 0.3.0 for Ruby.EPSS 2.9%

Source: NIST National Vulnerability Database (record CVE-2025-27220), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.