CVE-2026-33846
HighCVSS 7.5Exploitation Probability (EPSS)
Elevated risk68th percentile - higher than 68% of all known CVEs
Summary
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. An attacker can exploit this by sending crafted DTLS fragments with conflicting message_length values, causing an out-of-bounds write on the heap.
Risk Assessment
The vulnerability allows remote unauthenticated attackers to cause application crashes or potential memory corruption via the DTLS handshake path, which could lead to code execution or denial of service.
Recommendation
Update GnuTLS to the latest patched version immediately. As a temporary mitigation, restrict access to DTLS services and monitor network traffic for anomalous handshake fragments.
Other vulnerabilities in GnuTLS
See all- CVE-2016-4456High
The 'GNUTLS_KEYLOGFILE' environment variable in gnutls 3.4.12 allows remote attackers to overwrite and corrupt arbitrary files in the filesystem.
- CVE-2017-7507High
GnuTLS version 3.5.12 and earlier is vulnerable to a NULL pointer dereference while decoding a status response TLS extension with valid contents. This could lead to a crash of the GnuTLS server application.
- CVE-2017-7869High
GnuTLS before February 20, 2017, has an out-of-bounds write caused by an integer overflow and heap-based buffer overflow related to the cdk_pkt_read function in opencdk/read-packet.c. This issue is a subset of the vendor's GNUTLS-SA-2017-3 report and is fixed in version 3.5.10.
- CVE-2017-5335High
The stream reading functions in lib/opencdk/read-packet.c in GnuTLS before 3.3.26 and 3.5.x before 3.5.8 allow remote attackers to cause a denial of service (out-of-memory error and crash) via a crafted OpenPGP certificate.
- CVE-2016-7444High
The gnutls_ocsp_resp_check_crt function in GnuTLS before 3.4.15 and 3.5.x before 3.5.4 does not verify the serial length of an OCSP response, which might allow remote attackers to bypass an intended certificate validation mechanism.
- CVE-2015-3308High
A double free vulnerability in lib/x509/x509_ext.c in GnuTLS before version 3.3.14 allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted CRL distribution point.
- CVE-2024-28834Medium
A flaw was found in GnuTLS related to the Minerva attack, a cryptographic vulnerability that exploits deterministic behavior, leading to side-channel leaks. In specific scenarios, such as using the GNUTLS_PRIVKEY_FLAG_REPRODUCIBLE flag, it can result in a noticeable step in nonce values.
- CVE-2017-5337Critical
Multiple heap-based buffer overflows in the read_attribute function in GnuTLS before 3.3.26 and 3.5.x before 3.5.8 allow remote attackers to have unspecified impact via a crafted OpenPGP certificate.
- CVE-2017-5336Critical
A stack-based buffer overflow in the cdk_pk_get_keyid function in lib/opencdk/pubkey.c in GnuTLS before 3.3.26 and 3.5.x before 3.5.8 allows remote attackers to have unspecified impact via a crafted OpenPGP certificate.
- CVE-2017-5334Critical
A double free vulnerability in the gnutls_x509_ext_import_proxy function in GnuTLS before 3.3.26 and 3.5.x before 3.5.8 allows remote attackers to have unspecified impact via crafted policy language information in an X.509 certificate with a Proxy Certificate Information extension.
Original NVD description (English source)
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.