{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata — refreshed continuously.","feed_url":"https://feed.craftedsignal.io/tags/dtls/","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cves":[{"cvss":7.5,"id":"CVE-2026-33846"}],"_cs_exploited":false,"_cs_products":["GnuTLS"],"_cs_severities":["high"],"_cs_tags":["cve-2026-33846","dtls","heap overflow","gnutls","network"],"_cs_type":"advisory","_cs_vendors":["GnuTLS"],"content_html":"\u003cp\u003eA heap buffer overflow vulnerability has been identified in the DTLS handshake fragment reassembly logic of GnuTLS. The vulnerability, tracked as CVE-2026-33846, resides within the \u003ccode\u003emerge_handshake_packet()\u003c/code\u003e function. This function is responsible for matching and merging incoming DTLS handshake fragments. The core issue is the lack of validation for the \u003ccode\u003emessage_length\u003c/code\u003e field across different fragments belonging to the same logical message. An attacker can exploit this flaw by transmitting malicious DTLS fragments that contain inconsistent \u003ccode\u003emessage_length\u003c/code\u003e values. This inconsistency leads the GnuTLS implementation to allocate a buffer based on a smaller, initial fragment but subsequently attempts to write data beyond the allocated buffer\u0026rsquo;s boundaries using the larger, conflicting fragments. This out-of-bounds write on the heap can be triggered remotely without requiring any form of authentication, making it a critical vulnerability. Successful exploitation can lead to application crashes or, potentially, arbitrary memory corruption.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAttacker initiates a DTLS handshake with a vulnerable GnuTLS server.\u003c/li\u003e\n\u003cli\u003eThe attacker sends a first DTLS handshake fragment with a small \u003ccode\u003emessage_length\u003c/code\u003e value.\u003c/li\u003e\n\u003cli\u003eThe vulnerable \u003ccode\u003emerge_handshake_packet()\u003c/code\u003e function allocates a heap buffer based on the initial, smaller \u003ccode\u003emessage_length\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eAttacker sends a subsequent DTLS handshake fragment for the same handshake message with a larger, inconsistent \u003ccode\u003emessage_length\u003c/code\u003e value.\u003c/li\u003e\n\u003cli\u003e\u003ccode\u003emerge_handshake_packet()\u003c/code\u003e incorrectly merges the second fragment into the allocated buffer without proper bounds checking.\u003c/li\u003e\n\u003cli\u003eThe write operation overflows the allocated heap buffer, corrupting adjacent memory.\u003c/li\u003e\n\u003cli\u003eThe application crashes due to memory corruption, or the attacker potentially gains further control.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-33846 can lead to denial-of-service conditions due to application crashes. Memory corruption could allow for arbitrary code execution, but this is a less likely outcome. Given the widespread use of GnuTLS in various applications and systems, a large number of services could be impacted.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eMonitor network traffic for DTLS handshakes with inconsistent \u003ccode\u003emessage_length\u003c/code\u003e values in fragmented handshake messages using the provided Sigma rule \u003ccode\u003eDetect DTLS Handshake Fragment Length Mismatch\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eApply available patches from GnuTLS to remediate CVE-2026-33846.\u003c/li\u003e\n\u003cli\u003eImplement rate limiting for DTLS handshake requests to mitigate potential denial-of-service attacks.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-03T12:00:00Z","date_published":"2024-01-03T12:00:00Z","id":"/briefs/2024-01-03-gnutls-dtls-overflow/","summary":"A heap buffer overflow vulnerability, CVE-2026-33846, exists in the DTLS handshake fragment reassembly logic of GnuTLS, allowing unauthenticated remote attackers to cause application crashes or potential memory corruption by sending crafted DTLS fragments with conflicting message lengths.","title":"GnuTLS DTLS Handshake Heap Overflow Vulnerability (CVE-2026-33846)","url":"https://feed.craftedsignal.io/briefs/2024-01-03-gnutls-dtls-overflow/"}],"language":"en","title":"CraftedSignal Threat Feed — Dtls","version":"https://jsonfeed.org/version/1.1"}