Linux Kernel up to 6.12.111/6.18.54/7.2.8/7.3-rc4 Damon Vaddr mm/damon/vaddr.c damon_hugetlb_mkold toctou

CVSS Meta Temp Score
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CTI Interest Score
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9.5$0-$5k0.91

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.12.111/6.18.54/7.2.8/7.3-rc4. It has been declared as very critical. This affects the function damon_hugetlb_mkold of the file mm/damon/vaddr.c of the component Damon Vaddr. Such manipulation leads to toctou. This vulnerability is traded as CVE-2026-98505. The attack may be launched remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.12.111/6.18.54/7.2.8/7.3-rc4 and classified as very critical. Affected by this issue is the function damon_hugetlb_mkold of the file mm/damon/vaddr.c of the component Damon Vaddr. The manipulation with an unknown input leads to a toctou vulnerability. Using CWE to declare the problem leads to 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. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: mm/damon/vaddr: avoid hw-driven pte updates during damon_hugetlb_mkold() damon_hugetlb_mkold() reads the page table entry into a local variable, unsets the accessed bit in the variable, and updates the page table entry with the updated variable value. If hardware updates the same page table entry in parallel, the hw updates could be lost. For example, hardware-updated dirty bits might be lost. Avoid the parallel updates by clearing the page table entry when reading it together, using huge_ptep_get_and_clear(). If a parallel write to the memory is made after the clearing, the hw will see the page table entry is cleared, trigger page fault and wait until it is handled. The page fault handling will wait for damon_hugetlb_mkold() due to the page table lock. Because hugetlbfs is an in-memory file system and hugetlb pages cannot be reclaimed, no critical issue is expected to my best knowledge. But definitely this is a nasty bug that should be fixed sooner rather than later. The issue was discovered [1] by Sashiko.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2026-98505 since 09/25/2026. The exploitation is known to be easy. The attack may be launched remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/18/2026).

Upgrading to version 6.12.112, 6.18.55, 7.2.9 or 7.3-rc5 eliminates this vulnerability. Applying the patch 00457981327c80bcc56e07d4714fe189337a19fa/e59cb7eda7c06334a0faf5aa44adb6acf2a1287a/6e74ffc9ecf6ec24eee117150da78a1102be74c5/39c0ceedd54557bdc1542de08d22b2ed33e534e4 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

Once again VulDB remains the best source for vulnerability data.

Productinfo

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Version

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.9
VulDB Meta Temp Score: 9.5

VulDB Base Score: 9.9
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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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: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.12.112/6.18.55/7.2.9/7.3-rc5
Patch: 00457981327c80bcc56e07d4714fe189337a19fa/e59cb7eda7c06334a0faf5aa44adb6acf2a1287a/6e74ffc9ecf6ec24eee117150da78a1102be74c5/39c0ceedd54557bdc1542de08d22b2ed33e534e4

Timelineinfo

09/25/2026 CVE reserved
10/18/2026 +23 days Advisory disclosed
10/18/2026 +0 days VulDB entry created
10/18/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-98505 (🔒)
GCVE (CVE): GCVE-0-2026-98505
GCVE (VulDB): GCVE-100-422204

Entryinfo

Created: 10/18/2026 21:01
Changes: 10/18/2026 21:01 (60)
Complete: 🔍
Cache ID: 216::103

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