CVE-2026-89586 ata: libata-scsi: fix DSM TRIM for sector sizes larger than 2048 bytes
A logic error in the Linux kernel's libata-scsi module causes TRIM operations to fail on devices with sector sizes larger than 2048 bytes, leading to potential denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89586?
CVE-2026-89586 is a high-severity denial of service vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ata: libata-scsi: fix DSM TRIM for sector sizes larger than 2048 bytes
ata_scsi_write_same_xlat() translates a SCSI WRITE SAME command with the UNMAP bit set into an ATA DATA SET MANAGEMENT TRIM command. The TRIM descriptor is built by ata_format_dsm_trim_descr() into the 2048-byte ata_scsi_rbuf staging buffer, and the number of bytes copied is compared against the logical sector size by the caller:
size = ata_format_dsm_trim_descr(scmd, trmax, block, n_block); if (size != len) /* len == sdp->sector_size */ goto invalid_param_len;
ata_format_dsm_trim_descr() clamps the copy length to ATA_SCSI_RBUF_SIZE (2048). On a device whose logical sector size exceeds that (e.g. a 4Kn device, where sector_size == 4096) the function can never return more than 2048, while the caller expects it to return sector_size. The comparison therefore always fails, so every TRIM is rejected with "Parameter list length error" and WARN_ON() splats on each attempt. TRIM / discard is thus completely broken on such devices.
The descriptor was incorrectly sized from the logical sector size. A DSM TRIM payload is a list of 512-byte pages, each holding up to ATA_MAX_TRIM_RNUM (64) LBA Range Entries, and is independent of the logical sector size. The Block Limits VPD page already advertises a single such page as the maximum WRITE SAME length (65535 * ATA_MAX_TRIM_RNUM logical blocks), so the block layer never sends a request that needs more than one page.
Emit exactly one 512-byte page, independent of the logical sector size, and transfer only that page (COUNT == 1). For a 512-byte-sector device this is unchanged; devices with larger logical sectors now work instead of failing every TRIM.
Which versions are affected by CVE-2026-89586?
How do I fix CVE-2026-89586?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-89586 being exploited?
There is no known exploitation of CVE-2026-89586 in the wild and no public exploit code.
Sources
Also known as AZL-100178, BELL-CVE-2026-89586, DEBIAN-CVE-2026-89586, GHSA-4wqv-wrmf-6h4v, UBUNTU-CVE-2026-89586.