What’s Vulnerable › Vulnerabilities

CVE-2026-29076: cpp-httplib: Stack Overflow Denial of Service (DoS) via std::regex in multipart filename parsing

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-03-07 · updated 2026-06-17
• Weakness: CWE-674

Description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.37.0, cpp-httplib uses std::regex (libstdc++) to parse RFC 5987 encoded filename* values in multipart Content-Disposition headers. The regex engine in libstdc++ implements backtracking via deep recursion, consuming one stack frame per input character. An attacker can send a single HTTP POST request with a crafted filename* parameter that causes uncontrolled stack growth, resulting in a stack overflow (SIGSEGV) that crashes the server process. This issue has been patched in version 0.37.0.

Affected products

• yhirose cpp-httplib: before 0.37.0 — fixed in 0.37.0

How to fix

Upgrade to a fixed version: yhirose cpp-httplib 0.37.0. Check the vendor advisory for mitigations.

References

• https://github.com/yhirose/cpp-httplib/commit/de296af3eb5b0d5c116470e033db900e4812c5e6
• https://github.com/yhirose/cpp-httplib/releases/tag/v0.37.0
• https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-qq6v-r583-3h69

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