CVE-2026-46527 Null dereference in cpp-httplib
An attacker can crash the server by sending a malformed X-Forwarded-For header when trusted proxies are configured, causing a null dereference.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-46527?
CVE-2026-46527 is a high-severity vulnerability in yhirose cpp-httplib, published on 29 May 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 0.44.0, When the server has called Server::set_trusted_proxies() with a non-empty trusted-proxy list, an attacker can send an HTTP request that includes an X-Forwarded-For header whose value parses to no valid IP segments. The code path then executes get_client_ip(), which calls front() on an empty std::vector—undefined behavior in C++. On typical implementations this manifests as abnormal process termination (denial of service). With Sanitizers enabled, you get an explicit runtime diagnostic. This vulnerability is fixed in 0.44.0.
Weakness: CWE-476
Which versions are affected by CVE-2026-46527?
It affects 1 product.
Products include Yhirose Cpp-Httplib.
How do I fix CVE-2026-46527?
Upgrade to a fixed version.
Is CVE-2026-46527 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-46527 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-2026-32627 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
- CVE-2026-21428 cpp-httplib has CRLF injection in http headers
Sources
Also known as DEBIAN-CVE-2026-46527, GHSA-hg3g-vrg8-578g, UBUNTU-CVE-2026-46527.