Netty: Unix-socket fd receive leaks descriptors when peer sends two at once
CVE-2026-45536
What is CVE-2026-45536?
Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, netty_unix_socket_recvFd sets msg_control to char control[CMSG_SPACE(sizeof(int))] (line 940) — 24 bytes on 64-bit Linux. A peer-sent SCM_RIGHTS cmsg carrying two ints has cmsg_len = CMSG_LEN(8) = 24, which fits exactly with no MSG_CTRUNC, so the kernel installs both fds in the receiving process. The subsequent check cmsg->cmsg_len == CMSG_LEN(sizeof(int)) (line 972, expected 20) fails, the branch that would read the fd is skipped, and neither installed fd is closed. The for(;;) loop calls recvmsg again (non-blocking → EAGAIN → Java maps to 0 → read loop exits normally), leaving two leaked fds per message. There is no MSG_CTRUNC handling. Reachable via Epoll/KQueue DomainSocketChannel when the application opts into DomainSocketReadMode.FILE_DESCRIPTORS (non-default). Versions 4.1.135.Final and 4.2.15.Final patch the issue.
Affected Version(s)
netty >= 4.2.0.Final, < 4.2.15.Final < 4.2.0.Final, 4.2.15.Final
netty < 4.1.135.Final < 4.1.135.Final