Netty: Unix-socket fd receive leaks descriptors when peer sends two at once

Summary

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.

Timeline

1. Jun 12, 2026, 2:12 PM UTCCVE published
2. Jun 12, 2026, 3:05 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Jun 12, 2026, 3:05 PM UTCRecord last updated

Affected versions

• netty netty

  From 4.2.0.Final · fixed in 4.2.15.Final; fixed in 4.1.135.Final

• io.netty:netty-transport-native-epollMaven

  From 4.2.0.Final · fixed in 4.2.15.Final

• io.netty:netty-transport-native-kqueueMaven

  From 4.2.0.Final · fixed in 4.2.15.Final

• io.netty:netty-transport-native-kqueueMaven

  fixed in 4.1.135.Final

• io.netty:netty-transport-native-epollMaven

  fixed in 4.1.135.Final

References 3