# CVE-2026-18313: libpcap rpcapd memory leak in daemon_unpackapplyfilter

Source: https://junglewise.ai/threats/cve-2026-18313-libpcap-rpcapd-memory-leak-in-daemon-unpackapplyfilter  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-05. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-18313 · Severity: medium · CVSS 4.3 · Published 2026-09-05

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.

## Quick answers

**Is CVE-2026-18313 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-18313 being exploited in the wild.

**How severe is CVE-2026-18313?** Medium severity, with a CVSS score of 4.3, published 5 September 2026.

**Which products and versions are affected?** The Tcpdump Group libpcap.

**Is there a fix for CVE-2026-18313?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-18313 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-18313?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## 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

## References

- [https://github.com/the-tcpdump-group/libpcap/commit/f9775af1a0ec76db60c7213241e6b48f1be10ac7](https://github.com/the-tcpdump-group/libpcap/commit/f9775af1a0ec76db60c7213241e6b48f1be10ac7)