CVE-2026-89775

9.3 CRITICAL

Published 2026-09-16 · Updated 2026-09-16

AI risk analysis

Summary: The flaw allows for incorrect handling of negative S1 walk levels in VNCR TLB size evaluation, leading to potential security issues if exploited.
Exploitability: Exploitation requires specific conditions and is not trivial due to the need for precise control over MMU states.
Blast radius: If exploited, it could lead to unauthorized access or system instability, depending on the context of use.
Prioritized remediation: Update to a patched version of the Linux kernel as soon as possible.

kernelmmusecurity

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD description

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Handle negative S1 walk levels in VNCR TLB size evaluation Computing the effects of a TLB invalidation involves looking at the size of the mapping cached by the TLB. For S1 mappings such as VNCR, this is deducted from the combination of the base granule size and the mapping level. However, this implies that the S1 MMU is *on*. When the MMU is off, we indicate this with the level being set to a "creative" value of -127 (S1_MMU_DISABLED). This ends-up being misinterpreted by pgshift_level_to_ttl() as it doesn't handle negative levels at all (the level is immediately cast to a u8 and only the bottom two bits considered), leading to an invalidation size of 0. Not helpful. Tidy-up pgshift_level_to_ttl() to handle these negative levels, and ttl_to_size() to always return SZ_1G when no valid TTL is present. This allows the removal of open-coded checks for similar situations. Note that the check for a negative value not explicitely checking for S1_MMU_DISABLED is deliberate, so that actual negative levels introduced with LVA2 and D128 can take the same path if we ever support them.

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

Related CVEs

Related by shared AI tags and CWE weakness class. Browse the full archive.