CRLF Injection Affecting cpp-httplib package, versions <0.41.0+ds-3


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.38% (31st percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-CPPHTTPLIB-14843335
  • published2 Jan 2026
  • disclosed1 Jan 2026

Introduced: 1 Jan 2026

CVE-2026-21428  (opens in a new tab)
CWE-93  (opens in a new tab)

How to fix?

Upgrade Debian:unstable cpp-httplib to version 0.41.0+ds-3 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream cpp-httplib package and not the cpp-httplib package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.30.0, the write_headers function does not check for CR & LF characters in user supplied headers, allowing untrusted header value to escape header lines. This vulnerability allows attackers to add extra headers, modify request body unexpectedly & trigger an SSRF attack. When combined with a server that supports http1.1 pipelining (springboot, python twisted etc), this can be used for server side request forgery (SSRF). Version 0.30.0 fixes this issue.

CVSS Base Scores

version 3.1