Linux Kernel up to 7.1.3 userfaultfd userfaultfd_must_wait/userfaultfd_huge_must_wait encoding error

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9.5	$0-$5k	2.33-

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.1.3. It has been rated as very critical. The impacted element is the function userfaultfd_must_wait/userfaultfd_huge_must_wait of the component userfaultfd. Performing a manipulation results in encoding error. This vulnerability was named CVE-2026-64514. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability, which was classified as very critical, was found in Linux Kernel up to 7.1.3. This affects the function userfaultfd_must_wait/userfaultfd_huge_must_wait of the component userfaultfd. The manipulation with an unknown input leads to a encoding error vulnerability. CWE is classifying the issue as CWE-172. The product does not properly encode or decode the data, resulting in unexpected values. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: userfaultfd: gate must_wait writability check on pte_present() userfaultfd_must_wait() and userfaultfd_huge_must_wait() read the PTE without taking the page table lock and then apply pte_write() / huge_pte_write() to it. Those accessors decode bits from the present encoding only; on a swap or migration entry they read the offset bits that happen to share the same position and return an undefined result. The intent of the check is "is this fault still WP-blocked?". A non-marker swap entry means the page is in transit -- the userfault context the original fault delivered against is no longer the same, and the swap-in or migration completion path will re-deliver a fresh fault if userspace still needs to handle it. Worst case under the current code the garbage write bit says "wait", and the thread stays asleep until a UFFDIO_WAKE that may never arrive. Gate the writability check on pte_present() so the lockless re-check only inspects present-PTE bits when the entry is actually present. The non-present, non-marker case returns "don't wait" and lets the fault path retry.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-64514 since 07/19/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/26/2026).

Upgrading to version 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39, 7.1.4 or 7.2-rc1 eliminates this vulnerability. Applying the patch a5700a4c1c9099ac2ac73fe8a09cf059972e0d2f/d4026417e8184d13850a0bad4d96ceb6ed9f7152/29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0/5f4dbdb0a87596214076b20b94f2b71b522170b3/a6e9a4939e359599701b1da351e84f72e021443a/60d696a037eeeedfb57756dfe7ec08a1587c8631/710183888174639a15fcec16cd1af766b8480bb7/8e80af52db652fbc41320eee45a4f73bc029faf2 is able to eliminate this problem.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-48858). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.10.260
• 5.15.211
• 6.1.177
• 6.6.144
• 6.12.0
• 6.12.1
• 6.12.2
• 6.12.3
• 6.12.4
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• 6.12.88
• 6.12.89
• 6.12.90
• 6.12.91
• 6.12.92
• 6.12.93
• 6.12.94
• 6.12.95
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
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• 6.18.31
• 6.18.32
• 6.18.33
• 6.18.34
• 6.18.35
• 6.18.36
• 6.18.37
• 6.18.38
• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

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

Exploitinginfo

Class: Encoding error
CWE: CWE-172
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 5.10.261/5.15.212/6.1.178/6.6.145/6.12.96/6.18.39/7.1.4/7.2-rc1
Patch: a5700a4c1c9099ac2ac73fe8a09cf059972e0d2f/d4026417e8184d13850a0bad4d96ceb6ed9f7152/29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0/5f4dbdb0a87596214076b20b94f2b71b522170b3/a6e9a4939e359599701b1da351e84f72e021443a/60d696a037eeeedfb57756dfe7ec08a1587c8631/710183888174639a15fcec16cd1af766b8480bb7/8e80af52db652fbc41320eee45a4f73bc029faf2

Timelineinfo

07/19/2026 CVE reserved
07/25/2026 +6 days Advisory disclosed
07/25/2026 +0 days VulDB entry created
07/26/2026 +1 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-64514 (🔒)
GCVE (CVE): GCVE-0-2026-64514
GCVE (VulDB): GCVE-100-383313
EUVD: 🔒

Entryinfo

Created: 07/25/2026 19:27
Updated: 07/26/2026 02:04
Changes: 07/25/2026 19:27 (59), 07/26/2026 02:04 (1)
Complete: 🔍
Cache ID: 216::103

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

Discussion

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