Request smuggling via spaced header names
Published Nov 15, 2021 · Updated Apr 30, 2025
HTTP request smuggling in affected Node.js 12.x, 14.x, and 16.x releases allows remote attackers to desynchronize requests. The llhttp parser accepts an invalid space immediately after an HTTP header name and before its colon, causing intermediaries and Node.js to disagree about request boundaries. Exploitation requires an intermediary that parses the malformed header differently, enabling injected requests to bypass controls or poison caches.
Summary
What happened
HTTP request smuggling in affected Node.js 12.x, 14.x, and 16.x releases allows remote attackers to desynchronize requests. The llhttp parser accepts an invalid space immediately after an HTTP header name and before its colon, causing intermediaries and Node.js to disagree about request boundaries. Exploitation requires an intermediary that parses the malformed header differently, enabling injected requests to bypass controls or poison caches.
The record
- CVE
- CVE-2021-22959
- Published
- Nov 15, 2021
- Updated
- Apr 30, 2025
- Vendor
- Node.js
- Product
- Node.js
- Classifications
- CWE-444, CAPEC-33, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Nov 15, 2021CVE publishedPublication date reported by the CVE source.
- Apr 30, 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 <12.22.7
- Affected versionversion=13.0 <13.*
- Affected versionversion=14.0 <14.18.1
- Affected versionversion=15.0 <15.*
- Affected versionversion=16.0 <16.11.1
- 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?
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
- HackerOne report 1238709proof of concept · unverified
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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