CVE-2021-22960Network attack vector

Request smuggling via ignored chunk extensions

Published Nov 3, 2021 · Updated Apr 30, 2025

HTTP request smuggling in affected Node.js releases through 16.11.0 allows remote attackers to inject requests through a proxy. The embedded llhttp parse function ignores chunk extensions while parsing chunked request bodies, causing disagreement with an intermediary about request boundaries. Reachability requires an HTTP conversation traversing a proxy, reverse proxy, or load balancer before the Node.js server; successful smuggling injects an arbitrary request into the back-end connection.

CVSS severity6.5
Medium
EPSS probability2.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in affected Node.js releases through 16.11.0 allows remote attackers to inject requests through a proxy. The embedded llhttp parse function ignores chunk extensions while parsing chunked request bodies, causing disagreement with an intermediary about request boundaries. Reachability requires an HTTP conversation traversing a proxy, reverse proxy, or load balancer before the Node.js server; successful smuggling injects an arbitrary request into the back-end connection.

The record

CVE
CVE-2021-22960
Published
Nov 3, 2021
Updated
Apr 30, 2025
Vendor
Node.js
Product
Node.js
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Apr 30, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=10.0 <10.*
  2. Affected versionversion=11.0 <11.*
  3. Affected versionversion=12.0 <12.22.7
  4. Affected versionversion=13.0 <13.*
  5. Affected versionversion=14.0 <14.18.1
  6. Affected versionversion=15.0 <15.*
  7. Affected versionversion=16.0 <16.11.1
  8. Affected versionversion=4.0 <4.*
  9. Affected versionversion=5.0 <5.*
  10. Affected versionversion=6.0 <6.*
  11. Affected versionversion=7.0 <7.*
  12. Affected versionversion=8.0 <8.*
  13. Affected versionversion=9.0 <9.*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Node.js · Node.jsversion=10.0 <10.*; version=11.0 <11.*; version=12.0 <12.22.7; version=13.0 <13.*; version=14.0 <14.18.1; version=15.0 <15.*; version=16.0 <16.11.1; version=4.0 <4.*; version=5.0 <5.*; version=6.0 <6.*; version=7.0 <7.*; version=8.0 <8.*; version=9.0 <9.*

Published CVSS scores

6.4NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:P/I:P/A:N
6.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

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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