Request smuggling via malformed header termination
Published May 19, 2025 · Updated May 27, 2025
HTTP request smuggling in Node.js 20.0.0 through 20.19.1 allows remote attackers to bypass proxy access controls with malformed headers. The llhttp-based HTTP/1 parser accepts a header block ending in \r\n\rX where the protocol requires \r\n\r\n, causing it to disagree with stricter intermediaries about request boundaries. Exploitation requires a proxy or other front end that parses the same connection differently, after which unauthorized requests can reach protected handlers.
Summary
What happened
HTTP request smuggling in Node.js 20.0.0 through 20.19.1 allows remote attackers to bypass proxy access controls with malformed headers. The llhttp-based HTTP/1 parser accepts a header block ending in \r\n\rX where the protocol requires \r\n\r\n, causing it to disagree with stricter intermediaries about request boundaries. Exploitation requires a proxy or other front end that parses the same connection differently, after which unauthorized requests can reach protected handlers.
The record
- CVE
- CVE-2025-23167
- Published
- May 19, 2025
- Updated
- May 27, 2025
- Vendor
- Node.js
- Product
- Node.js
- Classifications
- CWE-444, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 19, 2025CVE publishedPublication date reported by the CVE source.
- May 27, 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=10.0 <10.*
- Affected versionversion=11.0 <11.*
- Affected versionversion=12.0 <12.*
- Affected versionversion=13.0 <13.*
- Affected versionversion=14.0 <14.*
- Affected versionversion=15.0 <15.*
- Affected versionversion=16.0 <16.*
- Affected versionversion=17.0 <17.*
- Affected versionversion=18.0 <18.*
- Affected versionversion=19.0 <19.*
- Affected versionversion=20.0 <=20.19.1
- Affected versionversion=4.0 <4.*
- Affected versionversion=5.0 <5.*
- Affected versionversion=6.0 <6.*
- Affected versionversion=7.0 <7.*
- Affected versionversion=8.0 <8.*
- Affected versionversion=9.0 <9.*
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
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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