Xen Grant Table toctou

Summaryinfo

A vulnerability classified as very critical was found in Xen. This affects an unknown part of the component Grant Table. The manipulation results in toctou. This vulnerability is known as CVE-2026-62435. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability, which was classified as very critical, was found in Xen (version unknown). Affected is an unknown function of the component Grant Table. The manipulation with an unknown input leads to a toctou vulnerability. CWE is classifying the issue as 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. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

[This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] With the introduction of Grant Table v2 came the requirement to be able to switch between versions. Switching from v1 to v2 reduces the number of valid grant references, as a bigger shared entry structure is then needed while the shared table doesn't change size. Switching from v2 back to v1 the status frames, which are separate in v2, go away. Code holding, but intermediately dropping and then re-acquiring the grant table lock, sometimes wrongly assumes that said properties wouldn't change across the window in time where the lock is not being held. The v1 -> v2 issue is CVE-2026-62435. The v2 -> v1 issue is CVE-2026-62436.

The advisory is shared for download at xenbits.xenproject.org. This vulnerability is traded as CVE-2026-62435 since 07/14/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 07/28/2026).

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

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Productinfo

Type

• Virtualization Software

Name

• Xen

License

• open-source

CPE 2.3info

• 🔒

CPE 2.2info

• 🔒

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