CVE-2026-89638: smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions
Noroxi assessment
Priority: Monitor (action score 31/100)
- 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).
- 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 2a5206992f526178881e8f5c4644757c336fb76d, 58b23fc9fb580432470d6c5da3c1e5660dba9fbc, 69bfe810ecd1e0387d8975d711cd326341d13c6e; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes.
- Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).
Low priority for now. Upgrade to Linux Linux 2a5206992f526178881e8f5c4644757c336fb76d, 58b23fc9fb580432470d6c5da3c1e5660dba9fbc, 69bfe810ecd1e0387d8975d711cd326341d13c6e; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes 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: smb: client: clear setuid/setgid bit on write with cifsacl/modefromsid/posix extensions When a file has the setuid or setgid bit set and is written to, the VFS strips those bits and issues a setattr with ATTR_KILL_SUID/ATTR_KILL_SGID together with an ATTR_MODE carrying the already-cleared mode. Both cifs_setattr_unix() and cifs_setattr_nounix() unconditionally dropped ATTR_MODE in that case: /* skip mode change if it's just for clearing setuid/setgid */ if (attrs->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) attrs->ia_valid &= ~ATTR_MODE; This is fine for the default mount, where the mode is only emulated via the DOS read-only attribute and cannot represent the setuid/setgid bits anyway. However, with the "cifsacl" or "modefromsid" mount options the mode is stored on the server through an ACL (id_mode_to_cifs_acl()), with the SMB3.1.1 POSIX extensions the mode is sent to the server directly, and with the SMB1 Unix extensions (cifs_setattr_unix) the mode is sent via CIFSSMBUnixSetPathInfo(). In all those cases dropping ATTR_MODE means the cleared mode is never pushed to the server, so the setuid/setgid bit survives the write. This is a security issue: on local filesystems the setuid bit is stripped when a file is written, but over these cifs.ko mounts the bit persists on the server, potentially allowing an unexpected privilege escalation on subsequent execution. Fix this in two places: 1. cifs_setattr_nounix(): only take the "skip mode change" shortcut when the mode is emulated via the DOS read-only attribute (i.e. neither cifsacl/modefromsid nor the SMB3.1.1 POSIX extensions are in effect), so that the cleared mode is propagated to the server in the ACL / POSIX cases. 2. cifs_setattr_unix(): this function is only called when Unix extensions are in effect, so the mode is always stored on the server. Remove the shortcut entirely so that the cleared mode is always pushed.
- Published
- Sep 11, 2026
- Updated
- Oct 30, 2026
- EPSS
- 0.1% · 7th percentile
- CWE
- —
Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.1%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · Linux
- 7.8
- 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.
—
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
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before ce0e675907b887db2b1e44a806118b0a7d8b6b18affected · git
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before a3a0cc83761e46a75b1ed6bfaf35961f2c211148affected · git
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before 2a5206992f526178881e8f5c4644757c336fb76daffected · git
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before 7ceb6f7cb8f8f2b094e0dcdaf75757775d231378affected · git
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before 58b23fc9fb580432470d6c5da3c1e5660dba9fbcaffected · git
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before b10015807e4c628095d1d1d1c9307efc8cdd9e1baffected · git
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before 69bfe810ecd1e0387d8975d711cd326341d13c6eaffected · git
- d32c4f2626acc385d5187bd5c0c24f442328dc60 and later · before b8e5dc4f95e5484159b343903f302eb6d783f2e6affected · 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:10 | kernel | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-core | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-core | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-devel | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-devel-matched | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules-core | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-debug-modules-extra | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-devel | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-devel-matched | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules-core | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-64k-modules-extra | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-abi-stablelists | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-core | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-cross-headers | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-debug | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-debug-core | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-debug-devel | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-debug-devel-matched | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-debug-modules | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
| AlmaLinux:10 | kernel-debug-modules-core | before 6.12.0-211.69.1.el10_2 | 6.12.0-211.69.1.el10_2 |
+96
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation40Plan
- CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment40Plan
- CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()40Plan
Published before and after this one in the same product
- ← EarlierCVE-2026-89636Sep 11, 2026 · smb: client: clear ce->tgthint in free_tgts()39Monitor
- ← EarlierCVE-2026-89637Sep 11, 2026 · smb: client: fix UAF and buffer leak in cifs_check_trans2() for malformed secondary T239Monitor
- Later →CVE-2026-89639Sep 11, 2026 · cifs: use cifs_invalidate_cache() in cifs_do_truncate() for O_TRUNC28Monitor
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 | 2a5206992f526178881e8f5c4644757c336fb76d | Vendor (CNA) |
| Linux Linux | 58b23fc9fb580432470d6c5da3c1e5660dba9fbc | Vendor (CNA) |
| Linux Linux | 69bfe810ecd1e0387d8975d711cd326341d13c6e | Vendor (CNA) |
| Linux Linux | 7ceb6f7cb8f8f2b094e0dcdaf75757775d231378 | Vendor (CNA) |
| Linux Linux | a3a0cc83761e46a75b1ed6bfaf35961f2c211148 | Vendor (CNA) |
| Linux Linux | b10015807e4c628095d1d1d1c9307efc8cdd9e1b | Vendor (CNA) |
| Linux Linux | b8e5dc4f95e5484159b343903f302eb6d783f2e6 | Vendor (CNA) |
| Linux Linux | ce0e675907b887db2b1e44a806118b0a7d8b6b18 | Vendor (CNA) |
| azl3 kernel 6.6.150.1-1 on Azure Linux 3.0 | — | Microsoft (MSRC) |
| azl3 kernel 6.6.152.1-1 on Azure Linux 3.0 | — | Microsoft (MSRC) |
| azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 | Release Notes | Microsoft (MSRC) |
| almalinux:bpftool | 4.18.0-553.178.1.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel | 4.18.0-553.178.1.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-core | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-core | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-devel | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-modules | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-debug-modules-extra | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-devel | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-modules | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| almalinux:kernel-rt-modules-extra | 4.18.0-553.178.1.rt7.519.el8_10 · AlmaLinux:8 | Package registry (OSV) |
| debian:linux | 6.12.113-1 · Debian:13 | Package registry (OSV) |
| debian:linux | 7.2.6-1 · Debian:14 | Package registry (OSV) |
| debian:linux-6.12 | 6.12.113-1~deb12u1 · Debian:12 | Package registry (OSV) |
| rocky linux:kernel | 0:4.18.0-553.178.1.el8_10 · Rocky Linux:8 | Package registry (OSV) |
| rocky linux:kernel-rt | 0:4.18.0-553.178.1.rt7.519.el8_10 · Rocky Linux:8 | Package 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.
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.
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).
National notice (Türkiye Cybersecurity Directorate / USOM)
Official security notices citing this record; remediation advice is on the agency's page.
- TR-26-1085 · Sep 14, 2026(Linux Kernel Güvenlik Bildirimi)
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
- high · data can be read
- 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
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
—
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
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/58b23fc9fb580432470d6c5da3c1e5660dba9fbc
- git.kernel.org/stable/c/69bfe810ecd1e0387d8975d711cd326341d13c6e
- git.kernel.org/stable/c/7ceb6f7cb8f8f2b094e0dcdaf75757775d231378
- git.kernel.org/stable/c/a3a0cc83761e46a75b1ed6bfaf35961f2c211148
- git.kernel.org/stable/c/b10015807e4c628095d1d1d1c9307efc8cdd9e1b
- git.kernel.org/stable/c/b8e5dc4f95e5484159b343903f302eb6d783f2e6
- git.kernel.org/stable/c/ce0e675907b887db2b1e44a806118b0a7d8b6b18
Vendor advisories and official records. Exploit/PoC links are deliberately left out.