CVE-2026-77358 cpp-httplib: Use-after-free of TLS session in WebSocketClient::shutdown_and_close()
A use-after-free in cpp-httplib's TLS WebSocket client allows attackers to cause crashes or potentially execute code during connection teardown.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-77358?
CVE-2026-77358 is a high-severity use after free vulnerability in yhirose cpp-httplib, published on 27 Aug 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++ header-only HTTP/HTTPS library. In versions 0.33.0 through 0.50.0, the TLS-enabled WebSocket client frees the TLS session before closing the WebSocket that still uses it, producing a use-after-free. In WebSocketClient::shutdown_and_close the SSL object is freed and the pointer cleared, but the subsequent WebSocket close still sends a close frame through the SSL socket stream, which holds a raw copy of the now-dangling session pointer and reads from and writes to the freed memory. The same freed-then-used ordering is reachable through the client's destructor and its connect path, so ordinary teardown of a secure WebSocket connection triggers the defect. This issue is fixed in version 0.50.1.
Weakness: CWE-416
Which versions are affected by CVE-2026-77358?
How do I fix CVE-2026-77358?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-77358 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77358 exists.
Sources
Also known as DEBIAN-CVE-2026-77358, GHSA-w7p7-f35j-mw7q, OESA-2026-3800, OESA-2026-3801, OESA-2026-3961, UBUNTU-CVE-2026-77358.