Xen Hypervisor - MSR Inverted Conditional Workaround Rework Failure
CVE-2026-79608 Published on October 13, 2026
x86/AMD: ineffectual Zenbleed workaround
The workaround for XSA-433 (Zenbleed, CVE-2023-20593) was later
re-worked to better integrate with other manipulations of the same MSR.
In this rework an inverted conditional was introduced, resulting in the
workaround to not be applied when needed and vice versa.
For more details, see:
http://xenbits.xen.org/xsa/advisory-433.html
Vulnerability Analysis
CVE-2026-79608 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Type
Always-Incorrect Control Flow Implementation
The code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated. This weakness captures cases in which a particular code segment is always incorrect with respect to the algorithm that it is implementing. For example, if a C programmer intends to include multiple statements in a single block but does not include the enclosing braces (CWE-483), then the logic is always incorrect. This issue is in contrast to most weaknesses in which the code usually behaves correctly, except when it is externally manipulated in malicious ways.
Products Associated with CVE-2026-79608
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