Daniel Stenberg

Use-After-Free in HTTP/2 Upload Leads to Potential RCE in curl: Detailed Analysis of CVE-2026-92392

In curl 8.23.0, developers fixed a high-severity Use-After-Free vulnerability tracked as CVE-2026-92392 that could allow remote code execution during HTTP/2 uploads. The flaw stems from a dangling pointer left on an easy handle after a server resets an HTTP/2 stream, which later gets dereferenced when the multi handle closes. An attacker controlling the server can influence memory contents to hijack a function pointer and execute arbitrary code, though successful exploitation requires precise conditions including upload size, memory layout, and knowledge of the target architecture. The issue was discovered by Luna Tong at Anthropic using their OSS Scanner and reported to the curl security team on September 15. The team accelerated the release cycle by two weeks to deliver the fix while maintaining standard procedures. curl maintainers continue reducing internal handle pointers in favor of identifiers and are adding more tests and static analysis to prevent similar memory-safety errors. The vulnerability highlights ongoing risks in C-based networking code handling multiplexed protocols like HTTP/2.