ublk: clear VM_MAYWRITE on read-only ublk char device mmap
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.
CVE-2026-89793
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-89793
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "71f28f3136aff5890cd56de78abc673f8393cad9",
"lessThan": "be41733c24be58e2a1ef718c80fafdfb98a40d5e",
"versionType": "git"
},
{
"status": "affected",
"version": "71f28f3136aff5890cd56de78abc673f8393cad9",
"lessThan": "5befd06a72216869b607cf7724a4f16c6a2d3999",
"versionType": "git"
},
{
"status": "affected",
"version": "71f28f3136aff5890cd56de78abc673f8393cad9",
"lessThan": "e373c1acdbcf88cec533ece9f589020adaed0a78",
"versionType": "git"
},
{
"status": "affected",
"version": "71f28f3136aff5890cd56de78abc673f8393cad9",
"lessThan": "fa5e1bc673ca59722608af67b27e65dba0c97926",
"versionType": "git"
},
{
"status": "affected",
"version": "71f28f3136aff5890cd56de78abc673f8393cad9",
"lessThan": "6e2b571b0a54755b06e092501913e1dfefe75d6c",
"versionType": "git"
}
],
"programFiles": [
"drivers/block/ublk_drv.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.0"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.0",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.110",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.5",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/block/ublk_drv.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-89793
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #36263 · Revision 1
- Added to Heist Feed
- Publisher date