Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-23456 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Linux Linux Kernel. Its CVSS base score is 8.2 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 43th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-23456 is an out-of-bounds read vulnerability in the Linux kernel's netfilter nf_conntrack_h323 helper. The issue occurs in the decode_int() function during the CONS case, where get_bits() reads a 2-bit length value, but the subsequent get_uint() call reads 1-4 bytes without verifying that sufficient data remains in the buffer. A malformed H.323/RAS packet can trigger a 1-4 byte slab-out-of-bounds read. The vulnerability carries a CVSS v3.1 base score of 8.2 (AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H).
Remote attackers require no privileges or user interaction to exploit this over the network with low complexity. By sending a specially crafted H.323/RAS packet, an attacker can cause the kernel to perform an out-of-bounds read, potentially leading to a denial of service through a kernel crash due to the high availability impact, along with limited confidentiality exposure from the read operation.
Mitigation involves applying kernel patches that add a boundary check for the required number of bytes after get_bits() and before calling get_uint(). Relevant stable backports are available in the following commits: https://git.kernel.org/stable/c/1e3a3593162c96e8a8de48b1e14f60c3b57fca8a, https://git.kernel.org/stable/c/41b417ff73a24b2c68134992cc44c88db27f482d, https://git.kernel.org/stable/c/52235bf88159a1ef16434ab49e47e99c8a09ab20, https://git.kernel.org/stable/c/6bce72daeccca9aa1746e92d6c3d4784e71f2ebb, and https://git.kernel.org/stable/c/774a434f8c9c8602a976b2536f65d0172a07f4d2.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-18712
Vulnerability Data
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case In decode_int(), the CONS case calls get_bits(bs, 2) to read a length value, then calls get_uint(bs, len) without checking that len…
more
bytes remain in the buffer. The existing boundary check only validates the 2 bits for get_bits(), not the subsequent 1-4 bytes that get_uint() reads. This allows a malformed H.323/RAS packet to cause a 1-4 byte slab-out-of-bounds read. Add a boundary check for len bytes after get_bits() and before get_uint().
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation directly finds out-of-bounds read flaws through static analysis, fuzzing, and dynamic bounds checks.
Secure engineering principles require bounds checking and memory-safe constructs that stop out-of-bounds reads from being introduced.
Process isolation confines the effects of an out-of-bounds read to the compromised process.
Input validation rejects malformed indices or lengths that would otherwise cause reads outside buffer bounds.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Vulnerability scanning and recording can discover instances of out-of-bounds reads after code is deployed.
Routine patching replaces vulnerable code containing out-of-bounds read flaws.
Secure-development practices such as bounds checking and memory-safe languages directly prevent out-of-bounds reads.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.
Secure development life cycle mandates input validation and bounds checking that directly prevent out-of-bounds reads.
Application security requirements include explicit bounds and memory-safety specifications that mitigate buffer over-reads.
Secure system architecture and engineering principles require memory-safe design patterns and runtime protections against out-of-bounds access.
Secure coding standards explicitly forbid unsafe pointer arithmetic and mandate bounds-checked reads, eliminating CWE-125.
Security testing in development and acceptance includes fuzzing and static analysis that detect out-of-bounds read defects before release.