CRLF injection in undici - CVE-2026-15157
Published: July 29, 2026
Vulnerability identifier: #VU140032
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-15157
CWE-ID: CWE-93
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Affected software:
undici
undici
Detailed vulnerability description
The vulnerability allows a remote attacker to inject arbitrary HTTP headers and potentially smuggle a second request past the upstream.
The vulnerability exists due to improper neutralization of CRLF sequences in lib/dispatcher/client-h1.js when processing a duck-typed blob-like body with an untrusted .type property through the HTTP/1.1 dispatcher. A remote attacker can supply crafted CRLF sequences in the .type value to inject arbitrary HTTP headers and potentially smuggle a second request past the upstream.
User interaction is required because exploitation occurs when an application passes untrusted input into a blob-like body's .type property. Native Blob is not affected, and fetch() is unaffected.
How to mitigate CVE-2026-15157
Install security update from vendor's website.