VulnerabilityPublished 24 Apr 2026Updated 4 Nov 2026

CVE-2026-31600: Linux kernel · arm64: mm: Handle invalid large leaf mappings correctly

Affects Linux kernelSource GCVE Database

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Authoritative record:CVE-2026-31600· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 7.0.0-28.28~24.04.1 : patch Linux kernel soon.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 7.0.0-28.28~24.04.1, 7.0.0-27.27, 7.0.0-1008.8 +6

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

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 4 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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.

What to do

Upgrade to a fixed release listed under Affected software.

Patches and advisories

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected <7.0.0-27.27	Fixed in 7.0.0-27.27
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected <7.0.0-1008.8	Fixed in 7.0.0-1008.8
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected <7.0.0-1010.10	Fixed in 7.0.0-1010.10
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected <7.0.0-1009.9	Fixed in 7.0.0-1009.9
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected <7.0.0-1007.7	Fixed in 7.0.0-1007.7
Ubuntu 26.04 LTSlinux-ibm`pkg:deb/ubuntu/linux-ibm?arch=source&distro=resolute`Other threats	Affected <7.0.0-1009.9	Fixed in 7.0.0-1009.9

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

AI-suggested

A patch is available and should be applied by upgrading to Linux kernel versions 7.0.0-27.27 or later as provided by the vendor. Ubuntu has released security updates addressing this issue in multiple kernel packages. After applying the update, a system reboot is required. Due to ABI changes, third-party kernel modules must be recompiled and reinstalled. No additional mitigation actions are indicated by the vendor advisory.

Description

CVE-2026-31600 is a vulnerability in the Linux kernel's ARM64 memory management subsystem. It involves improper handling of invalid large leaf page table entries (PTEs), which can cause kernel panics during certain operations such as booting a realm guest on specific hardware configurations. The flaw arises because parts of the kernel code were not designed to handle invalid large leaf mappings correctly. This issue has been addressed in Linux kernel versions starting from 7.0.0-27.27 and related releases.

Impact

The vulnerability can cause a kernel panic leading to denial of service on affected systems running vulnerable Linux kernel versions on ARM64 architecture. There is no indication of confidentiality or integrity impact, but the availability of the system is affected due to crashes. No known exploits in the wild have been reported.

Summary

The vulnerability CVE-2026-31600 affects the ARM64 memory management code in the Linux kernel. Historically, invalid page table entries (PTEs) in the linear map were marked by clearing the PTE_VALID bit, but large leaf mappings were not invalidated in this manner until a recent commit. As a result, various kernel components were not prepared to handle invalid large leaf mappings encoded in this way, leading to kernel panics under certain conditions, such as when booting a realm guest on a BBML2_NOABORT system. The issue manifests as a kernel paging request failure and an internal error causing a kernel panic. Multiple Linux kernel versions prior to 7.0.0-27.27 and related builds are affected. The problem has been fixed in Linux kernel versions 7.0.0-27.27 and later, with patches available from Ubuntu security notices.

References

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