CVE-2026-1525

Description

Undici allows duplicate HTTPContent-Lengthheaders when they are provided in an array with case-variant names (e.g.,Content-Lengthandcontent-length). This produces malformed HTTP/1.1 requests with multiple conflictingContent-Lengthvalues on the wire.Who is impacted: * Applications usingundici.request(),undici.Client, or similar low-level APIs with headers passed as flat arrays * Applications that accept user-controlled header names without case-normalizationPotential consequences: * Denial of Service: Strict HTTP parsers (proxies, servers) will reject requests with duplicateContent-Lengthheaders (400 Bad Request) * HTTP Request Smuggling: In deployments where an intermediary and backend interpret duplicate headers inconsistently (e.g., one uses the first value, the other uses the last), this can enable request smuggling attacks leading to ACL bypass, cache poisoning, or credential hijacking

Risk Information

Base Score

9.8

MODERATE

Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score

Exploitation Probability

0.016

Associated Vulnerability

Vulnerability	OS Platform
Multiple Vulnerabilities are affected in IBM App Connect Enterprise 13.0.6.2	Windows

Patch Details

No records found

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234