Quick answers
- Is CVE-2026-18238 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-18238 being exploited in the wild.
- How severe is CVE-2026-18238?
- Medium severity, with a CVSS score of 5, published 5 September 2026.
- Which products and versions are affected?
- tcpdump.org libpcap.
- Is there a fix for CVE-2026-18238?
- A patch was published on 2026-09-05. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-18238 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-18238?
- Check whether you run Tcpdump.Org Libpcap. 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
The vulnerability exists in the rpcap client code's handling of RPCAP_MSG_PACKET messages. The pcap_read_nocb_remote() function does not correctly validate that a complete RPCAP_MSG_PACKET header is present in the received message, and uses an incorrect length value to validate the declared message size. This allows a malicious rpcap server to send a crafted packet message that causes the client to over-read the buffer by up to 20 bytes, reading into adjacent process memory. The issue is network-reachable and requires only that the client connects to a malicious rpcap server. An integer overflow vulnerability in the UDP code path on 32-bit architectures is also mentioned. A fix is available in libpcap's repository.
Affected products
- tcpdump.org libpcap
Timeline
- 2026-09-05: disclosed
- 2026-09-05: patched