Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-31417 is a high-severity Wrap or Wraparound (CWE-191) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 37th 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-2026-31417 is an integer overflow vulnerability in the Linux kernel's X.25 protocol implementation within the net/x25 subsystem. It occurs when accumulating packet fragments, as the x25_sock.fraglen counter lacks bounds checking, potentially allowing it to exceed its limits. Additionally, fraglen is not reset during the purging of the fragment_queue in the x25_clear_queues() function, exacerbating the issue. The vulnerability affects Linux kernels that support the X.25 protocol and carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), indicating high availability impact without confidentiality or integrity effects.
A remote, unauthenticated attacker can exploit this vulnerability by sending crafted X.25 packets to a vulnerable system, triggering the overflow in fraglen during fragment accumulation. This leads to a kernel crash or denial of service, as the unchecked accumulation disrupts normal packet processing. No privileges or user interaction are required, and exploitation is straightforward over the network given the low attack complexity.
Mitigation is provided through upstream patches committed to Linux kernel stable trees, as documented in the referenced kernel.org git commits. These fixes add an explicit check to prevent x25_sock.fraglen from overflowing during packet accumulation and ensure fraglen is reset when purging the fragment_queue in x25_clear_queues(). Security practitioners should update to kernels incorporating these commits (e.g., 1734bd85c5e0, 4e2d1bcef78d, 6e568835ea54, 798d613afb64, 8c92969c197b) and consider disabling X.25 if unused, as it is a legacy protocol rarely required in modern environments.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-21938
Vulnerability Data
In the Linux kernel, the following vulnerability has been resolved: net/x25: Fix overflow when accumulating packets Add a check to ensure that `x25_sock.fraglen` does not overflow. The `fraglen` also needs to be resetted when purging `fragment_queue` in `x25_clear_queues()`.
- 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 static/dynamic analysis directly find integer underflow defects before code is released.
Security engineering principles require use of safe arithmetic constructs or language features that structurally eliminate integer underflow during subtraction.
Input validation can reject or sanitize values that would cause a subtraction to underflow the representable range.
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.
Secure SDLC practices directly prevent integer underflow defects via input validation, bounds checking, and static analysis.
Vulnerability scanning and code analysis can surface underflow flaws after they are introduced.
Routine patching can remediate known underflow bugs once they are discovered in deployed software.
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.
Security testing in development catches integer underflow defects before release.
Secure development lifecycle mandates input validation and arithmetic checks that prevent integer underflow.
Application security requirements include bounds checking and safe arithmetic to avoid underflow conditions.
Secure architecture principles require defensive coding patterns that mitigate integer wraparound risks.
Secure coding standards directly prescribe safe integer handling and overflow/underflow prevention.