CVE-2026-33845
Modified Modified - Updated After Analysis
DTLS Handshake Parsing Integer Underflow in GnuTLS

Publication date: 2026-04-30

Last updated on: 2026-06-02

Assigner: Red Hat, Inc.

Description
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.
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Meta Information
Published
2026-04-30
Last Modified
2026-06-02
Generated
2026-06-16
AI Q&A
2026-04-30
EPSS Evaluated
2026-06-15
NVD
CVE-2026-33845
EUVD
EUVD-2026-26392
Affected Vendors & Products
Showing 7 associated CPEs
Vendor Product Version / Range
redhat enterprise_linux 7.0
redhat enterprise_linux 6.0
gnu gnutls *
redhat enterprise_linux 8.0
redhat openshift_container_platform 4.0
redhat enterprise_linux 9.0
redhat enterprise_linux 10.0
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-191 The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.
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Executive Summary

This vulnerability exists in GnuTLS during the DTLS handshake process. It occurs when malformed fragments with zero length but a non-zero offset are processed, causing an integer underflow during the reassembly of these fragments. This leads to an out-of-bounds read, which is a type of memory access error.

The flaw can be triggered remotely by sending a zero-length fragment during a non-empty handshake, which causes the affected system to crash or become unresponsive.

Impact Analysis

This vulnerability can be exploited remotely to cause a Denial of Service (DoS) attack against systems using GnuTLS. The out-of-bounds read triggered by the malformed DTLS fragment can cause the system to crash or become unresponsive, impacting the availability of services relying on GnuTLS.

Additionally, there is a potential for information disclosure due to the out-of-bounds read, although the primary impact is on system availability.

Mitigation Strategies

To mitigate this vulnerability, it is recommended to monitor updates from your GnuTLS vendor and apply any patches or security updates as soon as they become available.

Additionally, consider restricting or filtering DTLS traffic from untrusted sources to reduce exposure to potential exploitation attempts.

Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

Detection Guidance

This vulnerability involves a flaw in GnuTLS DTLS handshake parsing triggered by malformed zero-length fragments with non-zero offset. Detection can focus on monitoring DTLS handshake traffic for such abnormal fragments.

One approach is to capture network traffic using tools like tcpdump or Wireshark and filter for DTLS handshake packets containing zero-length fragments.

  • Use tcpdump to capture DTLS traffic: tcpdump -i <interface> udp port 4433 -w dtls_capture.pcap
  • Analyze the capture with Wireshark, applying a filter for DTLS handshake messages and inspecting fragment lengths for zero-length fragments.

Additionally, monitoring system logs for crashes or unresponsiveness of applications using GnuTLS may indicate exploitation attempts.

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