Linux Kernel up to 7.3-rc1 ublk ublk_ch_mmap privileges management

CVSS Meta Temp Score
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CTI Interest Score
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4.2$0-$5k0.89

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.6.156/6.12.109/6.18.50/7.2.4/7.3-rc1 and classified as problematic. Impacted is the function ublk_ch_mmap of the component ublk. Performing a manipulation results in privileges management. This vulnerability is reported as CVE-2026-89793. The attack requires a local approach. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Linux Kernel up to 6.6.156/6.12.109/6.18.50/7.2.4/7.3-rc1. This affects the function ublk_ch_mmap of the component ublk. The manipulation with an unknown input leads to a privileges management vulnerability. CWE is classifying the issue as CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. 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: ublk: clear VM_MAYWRITE on read-only ublk char device mmap ublk_ch_mmap() rejects mmap requests with VM_WRITE set, but never clears VM_MAYWRITE on the resulting read-only mapping. This allows a userspace daemon to mmap the per-queue command buffer PROT_READ, then upgrade it to PROT_WRITE via mprotect(), since VM_MAYWRITE was never cleared. The command buffer holds struct ublksrv_io_desc entries that are kernel-written ABI; a writable mapping lets an unprivileged daemon process corrupt fields such as addr, op_flags, nr_sectors, and start_sector. Same bug class as the drm/panthor and drm/vc4 VM_MAYWRITE fixes, and the 2026-08-13 ptp/vmclock fix (a5edadbae57e). Verified via mprotect() PoC: before the fix, a PROT_READ mapping can be upgraded to PROT_READ|PROT_WRITE and a write into the command buffer corrupts io_desc fields (confirmed under KASAN). After the fix, mprotect() returns -EACCES.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-89793 since 09/11/2026. The exploitability is told to be easy. An attack has to be approached locally. 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 09/16/2026). MITRE ATT&CK project uses the attack technique T1068 for this issue.

Upgrading to version 6.6.157, 6.12.110, 6.18.51, 7.2.5 or 7.3-rc2 eliminates this vulnerability. Applying the patch be41733c24be58e2a1ef718c80fafdfb98a40d5e/5befd06a72216869b607cf7724a4f16c6a2d3999/e373c1acdbcf88cec533ece9f589020adaed0a78/fa5e1bc673ca59722608af67b27e65dba0c97926/6e2b571b0a54755b06e092501913e1dfefe75d6c 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: 4.4
VulDB Meta Temp Score: 4.2

VulDB Base Score: 4.4
VulDB Temp Score: 4.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

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

Exploitinginfo

Class: Privileges management
CWE: CWE-269 / CWE-266
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

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 6.6.157/6.12.110/6.18.51/7.2.5/7.3-rc2
Patch: be41733c24be58e2a1ef718c80fafdfb98a40d5e/5befd06a72216869b607cf7724a4f16c6a2d3999/e373c1acdbcf88cec533ece9f589020adaed0a78/fa5e1bc673ca59722608af67b27e65dba0c97926/6e2b571b0a54755b06e092501913e1dfefe75d6c

Timelineinfo

09/11/2026 CVE reserved
09/16/2026 +5 days Advisory disclosed
09/16/2026 +0 days VulDB entry created
09/16/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-89793 (🔒)
GCVE (CVE): GCVE-0-2026-89793
GCVE (VulDB): GCVE-100-405597

Entryinfo

Created: 09/16/2026 12:04
Changes: 09/16/2026 12:04 (59)
Complete: 🔍
Cache ID: 216::103

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