CVE-2026-89793

CVE CVE-2026-89793EUVD EUVD-2026-80589Published 2026-09-16T09:54:33.000ZLast changed 2026-09-16T14:38:42.000ZCVSS 7.8

What the advisory describes

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.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

Linux — Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <6e2b571b0a54755b06e092501913e1dfefe75d6c; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <fa5e1bc673ca59722608af67b27e65dba0c97926; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <e373c1acdbcf88cec533ece9f589020adaed0a78; patch: 6.12.110; 0 <6.6.157; patch: 7.2.5; patch: 6.18.51; 0 <6.18.51; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <5befd06a72216869b607cf7724a4f16c6a2d3999; 0 <6.12.110; patch: 7.3-rc2; patch: 6.6.157; 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <be41733c24be58e2a1ef718c80fafdfb98a40d5e; 0 <7.2.5

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

Linux — Linux

Does this concern one of your customers?

This page cannot answer that — it does not know your estate. Whoever has recorded their environments gets the answer the morning after publication, together with a paragraph they can forward to the customer unedited.

Try it for 28 days

Patchlage reports hits and suspected hits. About everything else this system says nothing — neither this page nor the situation report ever claims that an estate is safe.