CVE-2026-45372

What it is

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The validity check (is_field_value) is run before decoding, so encoded %0D%0A passes the check and is then expanded to a literal \r\n byte pair inside the stored header value. This vulnerability is fixed in 0.44.0.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-05-29 20:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-07-22 06:10 UTC Last updatedMost recent change to the record

Details

Published

2026-05-29 20:16 UTC

Last modified

2026-07-22 06:10 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-93

Record status

Modified

Affected

• Yhirose cpp-httplib < 0.44.0

Attack profile CVSS 3.1 · 9.9

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

Low

Integrity

High

Availability

Low