CVE-2025-27220Network attack vector

Service interruption via inefficient escapeElement regular expression

Published Mar 3, 2025 · Updated Nov 3, 2025

Regular expression denial of service in Ruby CGI on Ruby 3.1 and 3.2 allows remote attackers to interrupt services via crafted input. CGI::Util#escapeElement applies an inefficient regular expression to attacker-controlled element text, causing excessive backtracking and CPU consumption. A consuming application must pass the crafted input to this library method; no confidentiality or integrity impact is reported.

CVSS severity4.0
Medium
EPSS probability0.74%
Next 30 days · Sep 17, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Ruby CGI on Ruby 3.1 and 3.2 allows remote attackers to interrupt services via crafted input. CGI::Util#escapeElement applies an inefficient regular expression to attacker-controlled element text, causing excessive backtracking and CPU consumption. A consuming application must pass the crafted input to this library method; no confidentiality or integrity impact is reported.

The record

CVE
CVE-2025-27220
Published
Mar 3, 2025
Updated
Nov 3, 2025
Vendor
Ruby
Product
CGI
Classifications
CWE-1333, CAPEC-492, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 3, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <0.3.5.1
  2. Affected versionversion=0.3.6 <0.3.7
  3. Affected versionversion=0.4.0 <0.4.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Ruby · CGIversion=0 <0.3.5.1; version=0.3.6 <0.3.7; version=0.4.0 <0.4.2

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L
6.3GitHubCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
CAPEC-492Regular Expression Exponential Blowup
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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