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

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- irontec / sngrep (irontec/sngrep): ≥ 0; ≤ 1.9.0 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.8 (medium); 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; source: CNA: VulnCheck

- CVSS 3.1: 5.5 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H; source: CNA: VulnCheck

- CVSS 4.0: 6.8 (medium); 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 5.5 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-835

## Exploit evidence

- exploit: https://hackmd.io/@haindpwn/cve-2026-121943-121944-sngrep-sip-payload-missing-nul-oob-read (ADP: CISA-ADP)

## References

- https://github.com/irontec/sngrep/issues/589 (CNA: VulnCheck; issue-tracking)

- https://hackmd.io/@haindpwn/sngrep-sip-payload-missing-nul-oob-read (CNA: VulnCheck; third-party-advisory)

- https://github.com/irontec/sngrep/blob/v1.9.0/src/capture.c#L581-L598 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/sngrep-through-1.9.0-infinite-loop-dos-via-crafted-nflog-tlv (CNA: VulnCheck; third-party-advisory)

- https://hackmd.io/@haindpwn/cve-2026-121943-121944-sngrep-sip-payload-missing-nul-oob-read (ADP: CISA-ADP; exploit)

- https://github.com/irontec/sngrep/blob/v1.9.0/src/capture.c#L581-L598 (disclosure@vulncheck.com)

- https://github.com/irontec/sngrep/issues/589 (disclosure@vulncheck.com)

- https://hackmd.io/@haindpwn/sngrep-sip-payload-missing-nul-oob-read (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/sngrep-through-1.9.0-infinite-loop-dos-via-crafted-nflog-tlv (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121944; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121944; retrieved 2026-11-04; source updated 2026-11-04

Revision: 8436c593e1d2664959cb6af1e421569fee93c346d97f1e15d487d84bf930f0e6

Canonical: https://y2.dev/cve/CVE-2026-121944

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