CVE-2026-42009

Published May 18, 2026

Last updated 2 days ago

CVSS high 7.5
Tls

Overview

Description
A flaw was found in gnutls. A remote attacker could exploit an issue in the Datagram Transport Layer Security (DTLS) packet reordering logic. The comparator function, responsible for ordering DTLS packets by sequence numbers, did not correctly handle packets with duplicate sequence numbers. This could lead to unstable packet ordering or undefined behavior, resulting in a denial of service.
Source
secalert@redhat.com
NVD status
Undergoing Analysis

Risk scores

CVSS 3.1

Type
Secondary
Base score
7.5
Impact score
3.6
Exploitability score
3.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Severity
HIGH

Weaknesses

secalert@redhat.com
CWE-475

Social media

Hype score
Not currently trending

  1. ⚡ New CVE Alert: CVE-2026-42009 📊 Severity: 7.5 🚨 Risk Level: High 🧩 Affects: Multiple / Unspecified Products Reference: https://t.co/3YLR52MUfV #CVE-2026-42009 #CVE #High  #CyberSecurity #InfoSec https://t.co/9W2L6Yoaw8

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    18 May 2026

    46 Impressions

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  2. A flaw was found in gnutls. This vulnerability occurs because permitted name constraints were incorrectly ignored when previous Certificate Authorities (CAs) only had excluded name constraints. A remote attacker could exploit this to bypass critical name constraint checks during certificate validation. This bypass could lead to the acceptance of invalid certificates, potentially enabling spoofing or man-in-the-middle attacks against affected systems.•CVE-2026-42011
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  4. A heap buffer overflow vulnerability exists in the DTLS handshake fragment reassembly logic of GnuTLS. The issue arises in merge_handshake_packet() where incoming handshake fragments are matched and merged based solely on handshake type, without validating that the message_length field remains consistent across all fragments of the same logical message. An attacker can exploit this by sending crafted DTLS fragments with conflicting message_length values, causing the implementation to allocate a buffer based on a smaller initial fragment and subsequently write beyond its bounds using larger, inconsistent fragments. Because the merge operation does not enforce proper bounds checking against the allocated buffer size, this results in an out-of-bounds write on the heap. The vulnerability is remotely exploitable without authentication via the DTLS handshake path and can lead to application crashes or potential memory corruption.•CVE-2026-33846
  5. A flaw in GnuTLS DTLS handshake parsing allows malformed fragments with zero length and non-zero offset, leading to an integer underflow during reassembly and resulting in an out-of-bounds read. This issue is remotely exploitable and may cause information disclosure or denial of service.•CVE-2026-33845

References

Sources include official advisories and independent security research.