Xen IBPB initialization

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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4.1$0-$5k0.00

Summaryinfo

A vulnerability classified as problematic has been found in Xen. This affects an unknown function of the component IBPB Handler. Performing a manipulation results in an unknown weakness. This vulnerability is cataloged as CVE-2026-23553. There is no exploit available. It is recommended to apply a patch to fix this issue.

Detailsinfo

A vulnerability classified as problematic has been found in Xen (version now known). This affects some unknown processing of the component IBPB Handler. CWE is classifying the issue as CWE-665. The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used. The impact remains unknown. The summary by CVE is:

In the context switch logic Xen attempts to skip an IBPB in the case of a vCPU returning to a CPU on which it was the previous vCPU to run. While safe for Xen's isolation between vCPUs, this prevents the guest kernel correctly isolating between tasks. Consider: 1) vCPU runs on CPU A, running task 1. 2) vCPU moves to CPU B, idle gets scheduled on A. Xen skips IBPB. 3) On CPU B, guest kernel switches from task 1 to 2, issuing IBPB. 4) vCPU moves back to CPU A. Xen skips IBPB again. Now, task 2 is running on CPU A with task 1's training still in the BTB.

It is possible to read the advisory at xenbits.xen.org. This vulnerability is uniquely identified as CVE-2026-23553. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 02/10/2026).

The vulnerability scanner Nessus provides a plugin with the ID 296898 (Linux Distros Unpatched Vulnerability : CVE-2026-23553), which helps to determine the existence of the flaw in a target environment.

Applying a patch is able to eliminate this problem.

The vulnerability is also documented in the databases at Tenable (296898) and CERT Bund (WID-SEC-2026-0229). Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Fedora Linux
  • SUSE Linux
  • Citrix Systems XenServer
  • Open Source Xen

Productinfo

Type

Name

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.2
VulDB Meta Temp Score: 4.1

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔒
VulDB Reliability: 🔍

ADP CISA Base Score: 2.9
ADP CISA Vector: 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Initialization
CWE: CWE-665
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Partially

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 296898
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-23553

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Timelineinfo

01/27/2026 Advisory disclosed
01/27/2026 +0 days VulDB entry created
02/10/2026 +14 days VulDB entry last update

Sourcesinfo

Advisory: xenbits.xen.org
Status: Confirmed

CVE: CVE-2026-23553 (🔒)
GCVE (CVE): GCVE-0-2026-23553
GCVE (VulDB): GCVE-100-342999
CERT Bund: WID-SEC-2026-0229 - Citrix Systems XenServer und Xen: Schwachstelle ermöglicht Offenlegung von Informationen

Entryinfo

Created: 01/27/2026 14:16
Updated: 02/10/2026 11:13
Changes: 01/27/2026 14:16 (48), 01/28/2026 18:31 (2), 01/29/2026 07:17 (7), 01/29/2026 11:58 (2), 01/29/2026 16:51 (1), 02/10/2026 11:13 (11)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

Discussion

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