Detections
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Xen: x86: BTC/SRSO Fixes Not Fully Effective (XSA-446)

medium Nessus Plugin ID 186415

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Synopsis

The remote Xen hypervisor installation is missing a security update.

Description

The fixes for XSA-422 (Branch Type Confusion) and XSA-434 (Speculative Return Stack Overflow) are not IRQ-safe as it was believed that the mitigations were always operated in contexts with IRQs disabled. However due to an unanticipated interaction with XSA-254 (Meltdown), a race condition exists whereby a malicious guest can bypass BTC/SRSO protections.
As a result, an attacker in a PV guest can infer the contents of memory belonging to other guests.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Apply the appropriate patch according to the vendor advisory.

See Also

https://xenbits.xen.org/xsa/advisory-445.html

Plugin Details

Severity: Medium

ID: 186415

File Name: xen_server_XSA-446.nasl

Version: 1.5

Type: local

Family: Misc.

Published: 11/29/2023

Updated: 7/19/2024

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.6

CVSS v2

Risk Factor: Low

Base Score: 3.8

Temporal Score: 2.8

Vector: CVSS2#AV:L/AC:H/Au:S/C:C/I:N/A:N

CVSS Score Source: CVE-2023-46836

CVSS v3

Risk Factor: Medium

Base Score: 4.7

Temporal Score: 4.1

Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:xen:xen

Required KB Items: installed_sw/Xen Hypervisor, Settings/ParanoidReport

Exploit Ease: No known exploits are available

Patch Publication Date: 11/14/2023

Vulnerability Publication Date: 11/14/2023

Reference Information

CVE: CVE-2023-46836

IAVB: 2023-B-0090-S