CVE-2026-64298: NFSv4: include MAY_WRITE in open permission mask for O_TRUNC
Noroxi assessment
Priority: Monitor (action score 28/100)
- 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: 0.14% (FIRST EPSS).
- Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
- Fixed version: Linux Linux 22c1fd1355ad4ca27aa7f0fa02719122dd92d9de, 30fdf4df6c3c00efec947e4ddf97f0fdd4473628, 4817c8974315b666e895b7d1bb83cd3664c323b1; 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 22c1fd1355ad4ca27aa7f0fa02719122dd92d9de, 30fdf4df6c3c00efec947e4ddf97f0fdd4473628, 4817c8974315b666e895b7d1bb83cd3664c323b1; 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: NFSv4: include MAY_WRITE in open permission mask for O_TRUNC POSIX requires write permission to truncate a file, so an open() that specifies O_TRUNC must be authorized for write access regardless of the O_ACCMODE access mode. nfs_open_permission_mask() builds the access mask passed to nfs_may_open(), which is the local authorization gate for OPENs the client serves itself from a cached write delegation via the can_open_delegated() path in nfs4_try_open_cached(). The mask is derived from O_ACCMODE alone, so an open(O_RDONLY | O_TRUNC) against a file the caller cannot write requests only MAY_READ and passes the local check. The OPEN is then satisfied locally and the truncation is issued to the server as a SETATTR(size=0) over the delegation stateid, which the server accepts under standard write-delegation semantics. POSIX requires that this open fail with EACCES. Include MAY_WRITE in the mask whenever O_TRUNC is set so the local check matches the access the server would have enforced.
- Published
- Jul 25, 2026
- Updated
- Oct 19, 2026
- EPSS
- 0.1% · 3th percentile
- CWE
- CWE-862
Report tools
Action score
28
Monitor
Low priority for now.
- CVSS
- 28 / 40 · 7.1 / 10
- 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.
CNA vs NVD score
- NVD
- —
- CNA · Linux
- 7.1
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
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
If any of these changes, we'll tell you in the daily email digest.
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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.
We use this product, ask for helpAffected 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.
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- linux linux kernel2.6.24 and later · before 5.10.261
- linux linux kernel5.11 and later · before 5.15.212
- linux linux kernel5.16 and later · before 6.1.178
- linux linux kernel6.2 and later · before 6.6.145
- linux linux kernel6.7 and later · before 6.12.96
- linux linux kernel6.13 and later · before 6.18.39
- linux linux kernel6.19 and later · before 7.1.4
- linux linux kernel7.2
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
- 2.6.24affected
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before 4817c8974315b666e895b7d1bb83cd3664c323b1affected · git
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before cb148a2762d644bff1894728e8835a9a4b84f9eaaffected · git
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before 30fdf4df6c3c00efec947e4ddf97f0fdd4473628affected · git
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before 22c1fd1355ad4ca27aa7f0fa02719122dd92d9deaffected · git
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before 6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230affected · git
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before a937e92c1d00534b5c2e3e9f4381b7e988180797affected · git
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before e36501b7d4abdcd6d69a7cb901b2f286b7a3d041affected · git
- af22f94ae02ab9dd4fd7fe628c8434a59cc293be and later · before 5140f099ecd8a2f2808b7f7b720ee1bad8468974affected · git
- before 2.6.24not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:8 | bpftool | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-abi-stablelists | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-core | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-cross-headers | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-debug | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-debug-core | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-debug-devel | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-debug-modules | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-debug-modules-extra | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-devel | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-doc | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-headers | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-modules | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-modules-extra | before 4.18.0-553.159.1.el8_10 | 4.18.0-553.159.1.el8_10 |
| AlmaLinux:8 | kernel-rt | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-core | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-debug | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-debug-core | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-debug-devel | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-debug-modules | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-debug-modules-extra | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-devel | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
| AlmaLinux:8 | kernel-rt-modules | before 4.18.0-553.159.1.rt7.500.el8_10 | 4.18.0-553.159.1.rt7.500.el8_10 |
+96
Same product
linux: all recordsOther highest-scoring records for the same primary product.
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- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
Published before and after this one in the same product
- ← EarlierCVE-2026-64294Jul 25, 2026 · mm: do file ownership checks with the proper mount idmap22Monitor
- ← EarlierCVE-2026-64296Jul 25, 2026 · exfat: bound uniname advance in exfat_find_dir_entry()31Monitor
- Later →CVE-2026-64299Jul 25, 2026 · tracing: Prevent out-of-bounds read in glob matching28Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 22c1fd1355ad4ca27aa7f0fa02719122dd92d9de | Vendor (CNA) |
| Linux Linux | 30fdf4df6c3c00efec947e4ddf97f0fdd4473628 | Vendor (CNA) |
| Linux Linux | 4817c8974315b666e895b7d1bb83cd3664c323b1 | Vendor (CNA) |
| Linux Linux | 5140f099ecd8a2f2808b7f7b720ee1bad8468974 | Vendor (CNA) |
| Linux Linux | 6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230 | Vendor (CNA) |
| Linux Linux | a937e92c1d00534b5c2e3e9f4381b7e988180797 | Vendor (CNA) |
| Linux Linux | cb148a2762d644bff1894728e8835a9a4b84f9ea | Vendor (CNA) |
| Linux Linux | e36501b7d4abdcd6d69a7cb901b2f286b7a3d041 | Vendor (CNA) |
| azl3 kernel 6.6.144.1-1 on Azure Linux 3.0 | 6.6.145.2-1 · CBL-Mariner Releases | Microsoft (MSRC) |
| almalinux:bpftool | 4.18.0-553.159.1.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel | 4.18.0-553.159.1.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-core | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-core | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-devel | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-modules | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-modules-extra | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-devel | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-modules | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-modules-extra | 4.18.0-553.159.1.rt7.500.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| debian:linux | 6.1.180-1 · Debian:12 | Package registry (OSV) |
| debian:linux-6.12 | 6.12.100-1~deb12u1 · Debian:12 | Package registry (OSV) |
| red hat:kernel-rt | 0:4.18.0-553.159.1.rt7.500.el8_10 · Red Hat:enterprise_linux:8::nfv | Package registry (OSV) |
| red hat:kernel-rt-core | 0:4.18.0-553.159.1.rt7.500.el8_10 · Red Hat:enterprise_linux:8::nfv | Package registry (OSV) |
| red hat:kernel-rt-debug | 0:4.18.0-553.159.1.rt7.500.el8_10 · Red Hat:enterprise_linux:8::nfv | Package registry (OSV) |
| red hat:kernel-rt-debug-core | 0:4.18.0-553.159.1.rt7.500.el8_10 · Red Hat:enterprise_linux:8::nfv | Package registry (OSV) |
| red hat:kernel-rt-debug-debuginfo | 0:4.18.0-553.159.1.rt7.500.el8_10 · Red Hat:enterprise_linux:8::nfv | Package registry (OSV) |
| red hat:kernel-rt-debug-devel | 0:4.18.0-553.159.1.rt7.500.el8_10 · Red Hat:enterprise_linux:8::nfv | Package registry (OSV) |
| red hat:kernel-rt-debug-kvm | 0:4.18.0-553.159.1.rt7.500.el8_10 · Red Hat:enterprise_linux:8::nfv | Package registry (OSV) |
+7
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.
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 researchersFinders, 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.
- CVE-2026-638296 days apartnet: ip_gre: require CAP_NET_ADMIN in the device netns for changelink35Monitor
- CVE-2026-639216 days apartip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().35Monitor
- CVE-2026-639416 days apartKVM: arm64: Correctly cap ZCR_EL2 provided by a guest hypervisor35Monitor
- CVE-2026-640426 days apartvfio/pci: Check BAR resources before exporting a DMABUF35Monitor
- CVE-2026-4617458 days apartx86/CPU/AMD: Prevent improper isolation of shared resources in Zen2's op cache35Monitor
- CVE-2026-31788122 days apartxen/privcmd: restrict usage in unprivileged domU32Monitor
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
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-862 · Missing AuthorizationCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Change log
- SSVC exploitation— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (7 more)Show less
- git.kernel.org/stable/c/30fdf4df6c3c00efec947e4ddf97f0fdd4473628
- git.kernel.org/stable/c/4817c8974315b666e895b7d1bb83cd3664c323b1
- git.kernel.org/stable/c/5140f099ecd8a2f2808b7f7b720ee1bad8468974
- git.kernel.org/stable/c/6bd7d0a06b53c4e797e1a9cea0d2d41aa1b26230
- git.kernel.org/stable/c/a937e92c1d00534b5c2e3e9f4381b7e988180797
- git.kernel.org/stable/c/cb148a2762d644bff1894728e8835a9a4b84f9ea
- git.kernel.org/stable/c/e36501b7d4abdcd6d69a7cb901b2f286b7a3d041
Vendor advisories and official records. Exploit/PoC links are deliberately left out.