Xen TLB Flush toctou

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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9.9$5k-$25k1.22+

Summaryinfo

A vulnerability identified as very critical has been detected in Xen. This impacts an unknown function of the component TLB Flush. This manipulation causes toctou. This vulnerability appears as CVE-2026-79603. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability has been found in Xen (affected version not known) and classified as very critical. Affected by this vulnerability is some unknown functionality of the component TLB Flush. The manipulation with an unknown input leads to a toctou vulnerability. The CWE definition for the vulnerability is CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

x86 PV guests can free memory pages while still keeping a stale TLB entry pointing to them. A TLB flush is only issued by Xen (if needed) when the page is re-used. Since it's possible for the page to be scrubbed ahead of the TLB flush, there's a window where a PV guest can modify an already scrubbed page.

The advisory is shared at xenbits.xenproject.org. This vulnerability is known as CVE-2026-79603 since 08/25/2026. The exploitation appears to be easy. The attack can be launched remotely. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 09/08/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

Name

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.9
VulDB Meta Temp Score: 9.9

VulDB Base Score: 9.9
VulDB Temp Score: 9.9
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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

Exploitinginfo

Class: Toctou
CWE: CWE-367 / CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

08/25/2026 CVE reserved
09/08/2026 +14 days Advisory disclosed
09/08/2026 +0 days VulDB entry created
09/08/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: xenbits.xenproject.org
Status: Confirmed

CVE: CVE-2026-79603 (🔒)
GCVE (CVE): GCVE-0-2026-79603
GCVE (VulDB): GCVE-100-399793

Entryinfo

Created: 09/08/2026 14:37
Changes: 09/08/2026 14:37 (51)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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