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NVD / CVE Program· CNA Linux

CVE-2026-64514: userfaultfd: gate must_wait writability check on pte_present()

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
  • Fixed version: Linux Linux 29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0, 5f4dbdb0a87596214076b20b94f2b71b522170b3, 60d696a037eeeedfb57756dfe7ec08a1587c8631; azl3 kernel 6.6.144.1-1 on Azure Linux 3.0 6.6.145.2-1.

Low priority for now. Upgrade to Linux Linux 29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0, 5f4dbdb0a87596214076b20b94f2b71b522170b3, 60d696a037eeeedfb57756dfe7ec08a1587c8631; azl3 kernel 6.6.144.1-1 on Azure Linux 3.0 6.6.145.2-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

—No exploit Fix available
Published
Jul 25, 2026
Updated
Nov 6, 2026
EPSS
0.1% · 7th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 4.11affected
    • 369cd2121be440543280b91056de187f625d0dbb and later · before a5700a4c1c9099ac2ac73fe8a09cf059972e0d2faffected · git
    • 369cd2121be440543280b91056de187f625d0dbb and later · before d4026417e8184d13850a0bad4d96ceb6ed9f7152affected · git
    • 369cd2121be440543280b91056de187f625d0dbb and later · before 29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0affected · git
    • 369cd2121be440543280b91056de187f625d0dbb and later · before 5f4dbdb0a87596214076b20b94f2b71b522170b3affected · git
    • 369cd2121be440543280b91056de187f625d0dbb and later · before a6e9a4939e359599701b1da351e84f72e021443aaffected · git
    • 369cd2121be440543280b91056de187f625d0dbb and later · before 60d696a037eeeedfb57756dfe7ec08a1587c8631affected · git
    • 369cd2121be440543280b91056de187f625d0dbb and later · before 710183888174639a15fcec16cd1af766b8480bb7affected · git
    • 369cd2121be440543280b91056de187f625d0dbb and later · before 8e80af52db652fbc41320eee45a4f73bc029faf2affected · git
    • before 4.11not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.180-16.1.180-1
Debian:12linux-6.12before 6.12.100-1~deb12u16.12.100-1~deb12u1
Debian:13linuxbefore 6.12.96-16.12.96-1
Debian:14linuxbefore 7.1.4-17.1.4-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-64512Jul 25, 2026 · ACPI: CPPC: Suppress UBSAN warning caused by field misuse
    0Monitor
  • ← EarlierCVE-2026-64513Jul 25, 2026 · KVM: x86: Unconditionally recompute CR8 intercept on PPR update
    0Monitor
  • Later →CVE-2026-64515Jul 25, 2026 · wifi: mac80211: fix MLE defragmentation
    33Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux29e6f952c5fb7dc1d6b90fe5b7f36063d44ddae0Vendor (CNA)
Linux Linux5f4dbdb0a87596214076b20b94f2b71b522170b3Vendor (CNA)
Linux Linux60d696a037eeeedfb57756dfe7ec08a1587c8631Vendor (CNA)
Linux Linux710183888174639a15fcec16cd1af766b8480bb7Vendor (CNA)
Linux Linux8e80af52db652fbc41320eee45a4f73bc029faf2Vendor (CNA)
Linux Linuxa5700a4c1c9099ac2ac73fe8a09cf059972e0d2fVendor (CNA)
Linux Linuxa6e9a4939e359599701b1da351e84f72e021443aVendor (CNA)
Linux Linuxd4026417e8184d13850a0bad4d96ceb6ed9f7152Vendor (CNA)
azl3 kernel 6.6.144.1-1 on Azure Linux 3.06.6.145.2-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
debian:linux6.1.180-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.100-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records