Linux Kernel up to 6.12.108/6.18.49/7.2.3 NFSD nfsd_setattr toctou

CVSS Meta Temp Score
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CTI Interest Score
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5.2$0-$5k0.44+

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.12.108/6.18.49/7.2.3. It has been rated as problematic. This issue affects the function nfsd_setattr of the component NFSD. Performing a manipulation results in toctou. This vulnerability is cataloged as CVE-2026-89713. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.12.108/6.18.49/7.2.3. It has been classified as problematic. This affects the function nfsd_setattr of the component NFSD. The manipulation with an unknown input leads to a toctou vulnerability. CWE is classifying the issue as 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. This is going to have an impact on integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: NFSD: check truncate permission under inode lock nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC before it takes inode_lock(). The comparison uses the file size sampled by that unlocked read, but the actual ATTR_SIZE update is applied later under inode_lock() by notify_change(). This leaves a TOCTOU window for append-only files. If a client sends a SETATTR that does not shrink the file at the time of the unlocked sample, a concurrent append can extend the file before nfsd_setattr() takes inode_lock(). notify_change() then applies a real truncation without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS truncate syscall paths perform their own append-only checks before calling notify_change(), so NFSD must make this decision against the locked size it is about to change. Split the write-count acquisition from the truncation permission check. Keep get_write_access() before the locked setattr work, then recheck whether the requested size is below i_size_read(inode) after inode_lock() has been acquired and before notify_change(ATTR_SIZE). This also avoids the plain unlocked inode->i_size load.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-89713 since 09/11/2026. 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 09/11/2026).

Upgrading to version 6.12.109, 6.18.50, 7.2.4 or 7.3-rc1 eliminates this vulnerability. Applying the patch 3afa17d93ba8c925f49370c816c6dae5112d8c24/d8352da196349182e1afd5a93308256cddc0a97d/44086254479035de42ca3d286ecf25521d4e6325/b778e0e0a16759f22a70579c3cf8d254a40d4a7f is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.2

VulDB Base Score: 5.4
VulDB Temp Score: 5.2
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 6.12.109/6.18.50/7.2.4/7.3-rc1
Patch: 3afa17d93ba8c925f49370c816c6dae5112d8c24/d8352da196349182e1afd5a93308256cddc0a97d/44086254479035de42ca3d286ecf25521d4e6325/b778e0e0a16759f22a70579c3cf8d254a40d4a7f

Timelineinfo

09/11/2026 Advisory disclosed
09/11/2026 +0 days CVE reserved
09/11/2026 +0 days VulDB entry created
09/11/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-89713 (🔒)
GCVE (CVE): GCVE-0-2026-89713
GCVE (VulDB): GCVE-100-402549

Entryinfo

Created: 09/11/2026 22:12
Changes: 09/11/2026 22:12 (59)
Complete: 🔍
Cache ID: 216::103

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