What’s Vulnerable › Vulnerabilities

CVE-2026-77341: cpp-httplib: CRLF injection via unvalidated HTTP trailer headers in chunked response writing

• Severity: medium (CVSS 5.3 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-28 · updated 2026-09-09
• Weakness: CWE-93

Description

cpp-httplib is a C++ header-only HTTP/HTTPS library. In version 0.49.0, the chunked-response trailer output path writes trailer header names and values directly to the socket without validating them, allowing CRLF sequences in a trailer field to inject additional headers or split the HTTP response. Unlike every other header-writing path in the library, the trailer-writing code applies none of the field-name and field-value checks that reject carriage return and line feed, so an application that places attacker-influenced data into a chunked response trailer emits attacker-controlled CRLF onto the wire. This enables HTTP response splitting, letting an attacker forge response headers or inject a second response. This issue is fixed in version 0.50.0.

Affected products

• yhirose cpp-httplib: from 0.49.0, < 0.50.0

References

• https://github.com/yhirose/cpp-httplib/commit/568d434e72fc51729d0ad33abffb181e5f7a453d
• https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-2r2h-jc8w-w66c
• https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-2r2h-jc8w-w66c

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