Denial of service via super-linear cookie parsing
Published Mar 3, 2025 · Updated Nov 3, 2025
Denial of service in Ruby CGI 0.3.5 and earlier, 0.3.6, and 0.4.0 through 0.4.1 allows remote attackers to interrupt service. The CGI::Cookie.parse loop appends decoded characters with String#+, reallocating the accumulated value on each iteration and causing super-linear CPU use. Exploitation requires an application to pass an attacker-controlled cookie string to the method; resource exhaustion can stall the hosting process.
Summary
What happened
Denial of service in Ruby CGI 0.3.5 and earlier, 0.3.6, and 0.4.0 through 0.4.1 allows remote attackers to interrupt service. The CGI::Cookie.parse loop appends decoded characters with String#+, reallocating the accumulated value on each iteration and causing super-linear CPU use. Exploitation requires an application to pass an attacker-controlled cookie string to the method; resource exhaustion can stall the hosting process.
The record
- CVE
- CVE-2025-27219
- Published
- Mar 3, 2025
- Updated
- Nov 3, 2025
- Vendor
- Ruby
- Product
- CGI
- Classifications
- CWE-770, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 3, 2025CVE publishedPublication date reported by the CVE source.
- 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.
- Affected versionversion=0 <0.3.5.1
- Affected versionversion=0.3.6 <0.3.7
- Affected versionversion=0.4.0 <0.4.2
What conditions does exploitation require?
What is affected?
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.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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