VulnerabilityPublished 28 Jul 2026Updated 17 Oct 2026

CVE-2026-62436: Xen · [This CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] With the

Affects xenSource GCVE Database

Mentioned vulnerabilities

CVE-2026-62435

Not known to be exploited · CVSS 6.5 Medium.

Data as of 27 Oct 2026, 17:11 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-6j24-4j62-qj29

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.10xen`pkg:deb/ubuntu/xen?arch=source&distro=stonking`Other threats	Affected =4.20.2+7-g1badcf5035-2build2 =4.20.2+37-g61ff35323e-1ubuntu1 =4.20.3+127-gc42374a105-1	Fixed in–
Ubuntu 26.04 LTSxen`pkg:deb/ubuntu/xen?arch=source&distro=resolute`Other threats	Affected =4.20.0+68-g35cb38b222-1 =4.20.2+7-g1badcf5035-2 =4.20.2+7-g1badcf5035-2build2	Fixed in–
Ubuntu 24.04 LTSxen`pkg:deb/ubuntu/xen?arch=source&distro=noble`Other threats	Affected 4.17.2-1 – 4.17.3+10-g091466ba55-1.1ubuntu3 7 affected builds	Fixed in–
Ubuntu 22.04 LTSxen`pkg:deb/ubuntu/xen?arch=source&distro=jammy`Other threats	Affected =4.11.4+24-gddaaccbbab-1ubuntu2 =4.16.0-1~ubuntu2 =4.16.0-1~ubuntu2.1	Fixed in–
Ubuntu 20.04 LTSxen`pkg:deb/ubuntu/xen?arch=source&distro=focal`Other threats	Affected 4.9.2-0ubuntu2 – 4.11.3+24-g14b62ab3e5-1ubuntu2.3 7 affected builds	Fixed in–
Ubuntu 18.04 LTSxen`pkg:deb/ubuntu/xen?arch=source&distro=bionic`Other threats	Affected =4.9.0-0ubuntu3 =4.9.0-0ubuntu4 =4.9.2-0ubuntu1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until a fix is available, users should monitor vendor communications for updates. No specific workaround or mitigation is described in the provided data.

Description

[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.

Impact

The vulnerability can lead to a loss of confidentiality and availability due to inconsistent handling of grant table properties during version switching. This may cause incorrect memory access or denial of service conditions. There is no indication of privilege requirements or user interaction needed, and the attack vector is network-based. No known exploits are reported in the wild.

Summary

This vulnerability arises from improper handling of Grant Table version switching from v2 to v1. The code temporarily releases and reacquires the grant table lock but assumes that the properties of the grant table do not change during this window. However, the status frames present in v2 are removed in v1, leading to potential inconsistencies. This race condition can cause partial loss of integrity or availability in the system's shared memory management. The issue is distinct from CVE-2026-62435, which concerns the v1 to v2 switch.

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Architecture and Design
Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 29 Jul 2026, 11:23 UTC

WeaknessesCWE-362

Technical details

References

Community reviews

Related threats