---
id: "CVE-2026-121943"
kind: "vulnerability"
aliases: ["CVE-2026-121943"]
title: "sngrep: off-by-one SIP packet check lets remote senders crash it"
severity: "medium"
cvss: 6.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "self-hosted", "sip", "sngrep", "voip"]
not_affected_if: ["not-installed", "trusted-captures-only"]
published_at: "2026-11-04T13:17:28+00:00"
first_seen_at: "2026-11-04T13:27:03+00:00"
updated_at: "2026-11-04T13:28:09+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121943", "first_seen_at": "2026-11-04T13:27:03+00:00"}]
---

# sngrep: off-by-one SIP packet check lets remote senders crash it

sngrep is a terminal tool for capturing and viewing SIP (VoIP signalling) traffic. A crafted UDP or TCP SIP packet, or a malicious pcap file, can crash it or leak nearby stack memory into the displayed SIP fields.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `sngrep --version` and compare against the range in the advisory (through 1.9.0).
- Check whether sngrep runs on hosts that capture live SIP traffic from untrusted networks, or opens pcap files from outside sources.

## Timeline

- 2026-11-04T13:27:03+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121943

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/irontec-sngrep-through-1.9.0-out-of-bounds-stack-read-via-sip-check-packet

## From the sources

Irontec sngrep through 1.9.0 contains an out-of-bounds stack read vulnerability in sip_check_packet and sip_validate_packet caused by an off-by-one length check on 10240-byte SIP payloads. Remote attackers can send a crafted UDP or TCP SIP packet or supply a pcap file to crash sngrep or leak adjacent stack bytes into displayed SIP fields.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_