Security Bulletin
Summary
IBM DataPower Gateway has addressed multiple vulnerabilities in gnutls in versions 10.6.0.11 and 10.5.0.23
Vulnerability Details
CVEID: CVE-2026-3833
DESCRIPTION: A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of `nameConstraints` labels, specifically for `dNSName` (DNS) or `rfc822Name` (email) constraints within `excludedSubtrees` or `permittedSubtrees`. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.
CWE: CWE-178: Improper Handling of Case Sensitivity
CVSS Source: NVD
CVSS Base score: 7.4
CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N)
CVEID: CVE-2026-5260
DESCRIPTION: A flaw was found in libgnutls. A remote attacker, by sending an extremely short premaster secret during an RSA key exchange to a server using an RSA key backed by a PKCS#11 token, could trigger a short heap overread. This memory corruption vulnerability could lead to information disclosure.
CWE: CWE-126: Buffer Over-read
CVSS Source: secalert@redhat.com
CVSS Base score: 8.2
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H)
CVEID: CVE-2026-33845
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.
CWE: CWE-191: Integer Underflow (Wrap or Wraparound)
CVSS Source: NVD
CVSS Base score: 9.1
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H)
CVEID: CVE-2026-33846
DESCRIPTION: 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.
CWE: CWE-130: Improper Handling of Length Parameter Inconsistency
CVSS Source: secalert@redhat.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
CVEID: CVE-2026-42009
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.
CWE: CWE-475: Undefined Behavior for Input to API
CVSS Source: secalert@redhat.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
CVEID: CVE-2026-42010
DESCRIPTION: A flaw was found in gnutls. Servers configured with RSA-PSK (Rivest–Shamir–Adleman – Pre-Shared Key) wrongfully matched usernames containing a NUL character with truncated usernames. A remote attacker could exploit this by sending a specially crafted username, leading to an authentication bypass. This vulnerability allows an attacker to gain unauthorized access by circumventing the authentication process.
CWE: CWE-170: Improper Null Termination
CVSS Source: NVD
CVSS Base score: 9.8
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
CVEID: CVE-2026-42011
DESCRIPTION: 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.
CWE: CWE-295: Improper Certificate Validation
CVSS Source: secalert@redhat.com
CVSS Base score: 7.4
CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N)
CVEID: CVE-2026-42012
DESCRIPTION: A flaw was found in gnutls. A remote attacker could exploit this vulnerability by presenting a specially crafted certificate that contains Uniform Resource Identifier (URI) or Service (SRV) Subject Alternative Names (SANs). This could cause the certificate validation process to incorrectly fall back to checking DNS hostnames against the Common Name (CN), potentially allowing the attacker to spoof legitimate services or intercept sensitive information.
CWE: CWE-295: Improper Certificate Validation
CVSS Source: secalert@redhat.com
CVSS Base score: 7.1
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N)
CVEID: CVE-2026-42013
DESCRIPTION: A flaw was found in gnutls. When validating certificates, an oversized Subject Alternative Name (SAN) could cause the validation process to incorrectly fall back to checking the Common Name (CN) field. This could allow a remote attacker to bypass proper certificate validation, potentially leading to spoofing or man-in-the-middle attacks.
CWE: CWE-295: Improper Certificate Validation
CVSS Source: secalert@redhat.com
CVSS Base score: 8.2
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N)
CVEID: CVE-2026-42015
DESCRIPTION: A flaw was found in gnutls. An off-by-one error exists in the PKCS#12 bag element bounds check. This vulnerability allows an remote attacker to write past the internal array of a PKCS#12 bag when appending to a bag that already contains 32 elements. This memory corruption could lead to a denial of service (DoS) or potentially other unspecified impacts.
CWE: CWE-193: Off-by-one Error
CVSS Source: secalert@redhat.com
CVSS Base score: 5.3
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| IBM DataPower Gateway 10.6.0 | 10.6.0.0 - 10.6.0.10 |
| IBM DataPower Gateway 10.5.0 | 10.5.0.0 - 10.5.0.22 |
Remediation/Fixes
IBM strongly advises upgrading as soon as possible.
Known Issue: DT499976
| Affected Versions | Fixed in Release |
| IBM DataPower Gateway 10.6.0 10.6.0.0 - 10.6.0.10 | 10.6.0.11 |
| IBM DataPower Gateway 10.5.0 10.5.0.0 - 10.5.0.22 | 10.5.0.23 |
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
28 Sep 2026: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
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Document Information
Modified date:
28 September 2026
Initial Publish date:
28 September 2026
UID
ibm17289788