Vulnerability · Published Mar 27, 2026 · Assigned by GitHub_M

CVE-2026-33745cpp-httplib Client Leaks Authentication Credentials to Untrusted Hosts on Cross-Origin HTTP Redirect

High 7.4

In plain English

A high-severity information exposure in cpp-httplib from yhirose. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.4High

Exploit odds (30 days)0.3%top 81.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.39.0, the cpp-httplib HTTP client forwards stored Basic Auth, Bearer Token, and Digest Auth credentials to arbitrary hosts when following cross-origin HTTP redirects (301/302/307/308). A malicious or compromised server can redirect the client to an attacker-controlled host, which then receives the plaintext credentials in the `Authorization` header. Version 0.39.0 fixes the issue.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	cpp-httplib	no fix listed	DEBIAN-CVE-2026-33745
Debian:13	cpp-httplib	no fix listed	DEBIAN-CVE-2026-33745
Debian:14	cpp-httplib	0.41.0+ds-3	DEBIAN-CVE-2026-33745
Ubuntu:25.10	cpp-httplib	no fix listed	UBUNTU-CVE-2026-33745
Ubuntu:26.10	cpp-httplib	no fix listed	UBUNTU-CVE-2026-33745

Affected products (as reported)

Vendor	Product	Versions
yhirose	cpp-httplib	< 0.39.0

Weakness: CWE-200 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-6hrp-7fq9-3qv2 x_refsource_CONFIRM