# CVE-2026-6244: libpcap BPF interpreter division by zero in ALU instructions

Source: https://junglewise.ai/threats/cve-2026-6244-libpcap-bpf-interpreter-division-by-zero-in-alu-instructions  
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-2026-6244 · Severity: medium · CVSS 5.5 · Published 2026-09-05

libpcap is a network packet capture library used in tools like tcpdump and packet analysis software. A flaw in the BPF (Berkeley Packet Filter) interpreter fails to check for zero values when performing division or modulo operations, allowing a crafted filter program to trigger a division-by-zero error that crashes the application.

## Quick answers

**Is CVE-2026-6244 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-6244 being exploited in the wild.

**How severe is CVE-2026-6244?** Medium severity, with a CVSS score of 5.5, published 5 September 2026.

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

**Is there a fix for CVE-2026-6244?** A patch was published on 2026-09-05: Patch available via commit 98bb921 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-6244 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-6244?** 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

The vulnerability exists in the BPF interpreter's handling of 'div #k' and 'mod #k' ALU (arithmetic/logic unit) instructions, where k is an immediate constant value. While the interpreter correctly validates that the X register is non-zero for 'div x' and 'mod x' operations, it assumes k is never zero for immediate-value instructions. However, external filter programs passed via pcap_offline_filter() or bpf_filter() may not have been validated by libpcap, allowing an attacker to supply a crafted filter containing division or modulo by zero. Exploitation requires network reachability or the ability to supply a malicious filter program; when executed, this causes a SIGFPE signal that terminates the process. The fix treats 'div #k' and 'mod #k' the same as variable-operand instructions by explicitly checking for zero before division.

## Affected products

- The Tcpdump Group libpcap <UNKNOWN>

## Timeline

- 2026-09-05: disclosed
- 2026-09-05: patched: Patch available via commit 98bb921

## References

- [https://github.com/the-tcpdump-group/libpcap/commit/98bb921b141aa642faedbf2ac510541c76499a19](https://github.com/the-tcpdump-group/libpcap/commit/98bb921b141aa642faedbf2ac510541c76499a19)