GnuTLS Vulnerability CVE-2026-33845: Underflow Leads to Remote Exploitation

title: GnuTLS DTLS Handshake Underflow Exploit Attempt - CVE-2026-33845
id: scw-2026-04-30-ai-1
status: experimental
level: critical
description: |
  Detects attempts to exploit CVE-2026-33845 by looking for DTLS handshake traffic on port 443 with specific malformed fragment parameters (zero length and non-zero offset) that trigger the integer underflow vulnerability in GnuTLS. This is a direct indicator of an initial access attempt exploiting this specific flaw.
author: SCW Feed Engine (AI-generated)
date: 2026-04-30
references:
  - https://shimiscyberworld.com/posts/nvd-CVE-2026-33845/
tags:
  - attack.initial_access
  - attack.t1190
logsource:
    category: firewall
detection:
  selection:
      dst_port:
          - 443
      src_ip:
          - '0.0.0.0/0'
      dst_ip:
          - '0.0.0.0/0'
      action:
          - 'allow'
      uri|contains:
          - '/dtls/handshake'
      cs-uri-query|contains:
          - 'fragment_len=0&offset=1'
  condition: selection
falsepositives:
  - Legitimate administrative activity

Source: Shimi's Cyber World · License & reuse