CVE-2026-29076 cpp-httplib: Stack Overflow Denial of Service (DoS) via std::regex in multipart filename parsing
An attacker can crash the server by sending a crafted HTTP POST request with a malicious multipart filename, causing a stack overflow in the cpp-httplib library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-29076?
CVE-2026-29076 is a medium-severity denial of service vulnerability in yhirose cpp-httplib, published on 7 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-29076?
It affects 1 product.
Products include Yhirose Cpp-Httplib.
How do I fix CVE-2026-29076?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-29076 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-29076 exists.
Other vulnerabilities in yhirose cpp-httplib
- CVE-2025-66570 cpp-httplib Untrusted HTTP Header Handling: Internal Header Shadowing (REMOTE*/LOCAL*)
- CVE-2026-45372 cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection
- CVE-2026-46527 Null dereference in cpp-httplib
- CVE-2026-32627 cpp-httplib has a Silent TLS Certificate Verification Bypass on HTTPS Redirect via Proxy
- CVE-2026-22776 cpp-httplib vulnerable to a denial of service (DOS) using a zip bomb
Sources
Also known as DEBIAN-CVE-2026-29076, GHSA-qq6v-r583-3h69, UBUNTU-CVE-2026-29076.