Executive brief
rpcapd is the remote packet capture daemon shipped with libpcap, used for capturing network traffic over a network connection. A flaw causes the daemon to leak up to 65 KB of memory per request message from a client without ever freeing it; an attacker can trigger memory exhaustion and cause a denial of service by sending repeated malicious requests.
Technical details
A memory leak exists in the daemon_unpackapplyfilter() function in rpcapd, where temporary buffers up to 65536 bytes (8192 BPF instructions) allocated during processing of RPCAP_MSG_UPDATEFILTER_REQ and RPCAP_MSG_STARTCAP_REQ messages are never freed. The vulnerability occurs in the daemon.c component and is triggered by network requests from any client that establishes a connection. A malicious attacker can repeatedly send such messages to exhaust server memory and cause denial of service. The fix involves ensuring allocated memory is properly freed after use, and a patch has been committed to the libpcap repository.
Affected products
- The Tcpdump Group libpcap
Timeline
- 2026-09-05: disclosed