CVE-2026-77358: cpp-httplib: Use-after-free of TLS session in WebSocketClient::shutdown_and_close()
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::shutdownandclose 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
cpp-httplibto a version that resolves this vulnerability.Fixed in 0.50.1
Event History
Frequently Asked Questions
Which deployments are affected?
Applications using cpp-httplib versions 0.33.0 through 0.50.0 with the TLS-enabled WebSocket client are affected. The issue occurs during teardown of a secure WebSocket connection.
Does exploitation require an unusual shutdown sequence?
No. Ordinary secure WebSocket connection teardown can reach the freed-then-used TLS session ordering through WebSocketClient::shutdown_and_close(), the client destructor, and the connect path.
What should be done to remediate the issue?
Upgrade cpp-httplib to version 0.50.1, which fixes the TLS session lifetime ordering.