CVE-2026-72086 scsi: xen: scsiback: Free the command tag on the TMR submit-failure path
A local attacker in a pvSCSI guest can cause a denial of service by leaking command tags, stopping the LUN.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72086?
CVE-2026-72086 is a denial of service vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
scsi: xen: scsiback: Free the command tag on the TMR submit-failure path
scsiback_device_action() obtains a command tag in scsiback_get_pend_req() and submits a task-management request with target_submit_tmr(). When target_submit_tmr() fails it returns < 0 and scsiback jumps to the err: label, which sends a response but frees nothing, leaking the tag.
Impact: a pvSCSI guest can leak the command tags of a LUN's session, stopping the LUN, by issuing VSCSIIF_ACT_SCSI_ABORT or RESET requests whenever target_submit_tmr() fails.
transport_generic_free_cmd() cannot be used here. By the time target_submit_tmr() returns an error it has already run __target_init_cmd() (so se_cmd->cmd_kref is one, not zero), and on its target_get_sess_cmd() error path it has freed se_cmd->se_tmr_req via core_tmr_release_req() while leaving SCF_SCSI_TMR_CDB set and the pointer dangling. Letting the command release run target_free_cmd_mem() would then double-free se_tmr_req.
Use the same helper, which returns just the tag, on this path too.
Which versions are affected by CVE-2026-72086?
How do I fix CVE-2026-72086?
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-2026-72086 being exploited?
There is no known exploitation of CVE-2026-72086 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72086, DEBIAN-CVE-2026-72086, GHSA-mxg2-v7p6-pg5g, UBUNTU-CVE-2026-72086.