CVE-2026-21428

Publication date 1 January 2026

Last updated 10 July 2026

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
cpp-httplib	26.04 LTS resolute	Vulnerable
	25.10 questing	Ignored end of life, was needed
	25.04 plucky	Ignored end of life, was needs-triage
	24.04 LTS noble	Vulnerable
	22.04 LTS jammy	Vulnerable

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
cpp-httplib	Upstream: 98048a0

Severity score breakdown

CVSS version:

Base score 7.7 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Attack requirements	None
Privileges required	None
User interaction	None
Vulnerable system - Confidentiality impact	None
Vulnerable system - Integrity impact	High
Vulnerable system - Availability impact	None
Subsequent system - Confidentiality impact	None
Subsequent system - Integrity impact	None
Subsequent system - Availability impact	None

Scores

Parameter	Value
Base score	7.7 · High
Base + Threat score	-
Base + Environmental score	-
Base + Threat + Environmental score	-

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P

Base score 7.5 · High

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality impact	None
Integrity impact	High
Availability impact	None

Scores

Parameter	Value
Base score	7.5 · High
Exploitability score	-
Impact score	-

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