CVE-2026-1527Network attack vector

HTTP header injection via unvalidated upgrade value

Published Mar 12, 2026 · Updated Mar 12, 2026

CRLF injection in the client.request() upgrade option in Node.js Undici allows remote attackers to inject headers into outbound HTTP/1.1 requests. The HTTP/1.1 dispatcher appends the upgrade value directly to its header buffer without rejecting carriage-return or line-feed characters. Exploitation requires a consuming application to pass attacker-controlled input to client.request(); successful input can end the request and send chosen bytes to a reachable non-HTTP service.

CVSS severity4.2
Medium
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CRLF injection in the client.request() upgrade option in Node.js Undici allows remote attackers to inject headers into outbound HTTP/1.1 requests. The HTTP/1.1 dispatcher appends the upgrade value directly to its header buffer without rejecting carriage-return or line-feed characters. Exploitation requires a consuming application to pass attacker-controlled input to client.request(); successful input can end the request and send chosen bytes to a reachable non-HTTP service.

The record

CVE
CVE-2026-1527
Published
Mar 12, 2026
Updated
Mar 12, 2026
Vendor
Node.js
Product
Undici
Classifications
CWE-93
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 12, 2026Record 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=< 6.24.0; 7.0.0 < 7.24.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Node.js · Undiciversion=< 6.24.0; 7.0.0 < 7.24.0

Published CVSS scores

4.2GitHub Security AdvisoryCVSS:3.1/AV:N/AC:H/PR:N/UI:R/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 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-93Improper Neutralization of CRLF Sequences ('CRLF Injection')

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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