# CVE-2026-121944: sngrep infinite loop in capture_packet_reasm_ip

Source: https://junglewise.ai/threats/cve-2026-121944-sngrep-through-1-9-0-contains-an-infinite-loop-vulnerability-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-04. Updated: 2026-11-04  
License: CC BY 4.0 with a link back

CVE-2026-121944 · Severity: medium · CVSS 5.5 · Published 2026-11-04

sngrep is a SIP packet capture and flow viewing tool used by engineers to analyze VoIP call signaling. An attacker can craft a malicious pcap file that causes sngrep's packet processing thread to enter an infinite loop, consuming 100% CPU and making the application unresponsive. This allows denial of service by simply providing a pcap file with specially crafted NFLOG link-layer headers.

Technologies: [Irontec Sngrep](https://junglewise.ai/threats/technologies/sngrep). Vendors: [Irontec](https://junglewise.ai/threats/vendors/irontec).

## Quick answers

**Is CVE-2026-121944 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121944 being exploited in the wild.

**How severe is CVE-2026-121944?** Medium severity, with a CVSS score of 5.5, published 4 November 2026.

**Which products and versions are affected?** Irontec Sngrep through 1.9.0.

**Is there a fix for CVE-2026-121944?** No fixed version is recorded yet. Avoid processing untrusted pcap files with NFLOG link type, or restrict sngrep to live capture from trusted interfaces only; apply input validation to reject NFLOG packets with malformed TLV structures.</anigation>
</invoke> 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-2026-121944 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-121944?** Check whether you run Irontec Sngrep at an affected version. 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.

## How to fix


Avoid processing untrusted pcap files with NFLOG link type, or restrict sngrep to live capture from trusted interfaces only; apply input validation to reject NFLOG packets with malformed TLV structures.</anigation>
</invoke>

## Technical details

An infinite loop exists in capture_packet_reasm_ip() when processing NFLOG TLV (Type-Length-Value) structures; if a non-payload TLV has a length below 4 bytes, the cursor variable link_hl does not advance and the loop condition remains true indefinitely. The vulnerability is triggered when a pcap file specifies NFLOG as the link type (DLT_NFLOG, value 239) and contains a crafted TLV with insufficient length, causing the capture thread to spin without exiting.

## Affected products

- Irontec sngrep through 1.9.0

## Timeline

- 2026-11-04: disclosed
- 2026-10-21: other: vulnerability reported on GitHub issue #589

## References

- [https://github.com/irontec/sngrep/blob/v1.9.0/src/capture.c](https://github.com/irontec/sngrep/blob/v1.9.0/src/capture.c)
- [https://github.com/irontec/sngrep/issues/589](https://github.com/irontec/sngrep/issues/589)

## Related threats

- [Irontec sngrep out-of-bounds stack read in SIP parser](https://junglewise.ai/threats/cve-2026-121943-irontec-sngrep-through-1-9-0-contains-an-out-of-bounds-stack)
- [sngrep stack buffer overflow in SIP header formatting](https://junglewise.ai/threats/cve-2026-90558-sngrep-stack-buffer-overflow-in-sip-header-formatting)