# CVE-2026-72086: scsi: xen: scsiback: Free the command tag on the TMR submit-failure path

Status: published. Published: 2026-08-15. Updated: 2026-11-06.

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.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 2dbcdf33dbf61f44b29adb52338282c3d7840d0e; < 4567ce79fe2f84c3dcc3a91b22a377cf482d33ad (affected, git); ≥ 2dbcdf33dbf61f44b29adb52338282c3d7840d0e; < 6c01f0439098f00a64b246dc27479602201382f7 (affected, git); ≥ 2dbcdf33dbf61f44b29adb52338282c3d7840d0e; < 18d4f86816592586b38513543b5e1f9553bc271f (affected, git); ≥ 2dbcdf33dbf61f44b29adb52338282c3d7840d0e; < fbc1bdede66d0f2cde83b75d6524ce1a815bb69f (affected, git); ≥ 2dbcdf33dbf61f44b29adb52338282c3d7840d0e; < 255fb7b0cdc947b1c01929c7f133281342a3a6b5 (affected, git); ≥ 2dbcdf33dbf61f44b29adb52338282c3d7840d0e; < 1357fb32d42ad8da193e6da285f09e6452feabda (affected, git); ≥ 2dbcdf33dbf61f44b29adb52338282c3d7840d0e; < 66aefc277ebb796ec285d550305535dc3fc0179f (affected, git). Source: CNA: Linux
- Linux / Linux: 4.6 (affected); ≥ 0; < 4.6 (unaffected, semver); ≥ 5.15.212; ≤ 5.15.* (unaffected, semver); ≥ 6.1.178; ≤ 6.1.* (unaffected, semver); ≥ 6.6.145; ≤ 6.6.* (unaffected, semver); ≥ 6.12.97; ≤ 6.12.* (unaffected, semver); ≥ 6.18.40; ≤ 6.18.* (unaffected, semver); ≥ 7.1.5; ≤ 7.1.* (unaffected, semver); ≥ 7.2; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.21% as of 2026-11-06; percentile 11.44%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/4567ce79fe2f84c3dcc3a91b22a377cf482d33ad (CNA: Linux)

- https://git.kernel.org/stable/c/6c01f0439098f00a64b246dc27479602201382f7 (CNA: Linux)

- https://git.kernel.org/stable/c/18d4f86816592586b38513543b5e1f9553bc271f (CNA: Linux)

- https://git.kernel.org/stable/c/fbc1bdede66d0f2cde83b75d6524ce1a815bb69f (CNA: Linux)

- https://git.kernel.org/stable/c/255fb7b0cdc947b1c01929c7f133281342a3a6b5 (CNA: Linux)

- https://git.kernel.org/stable/c/1357fb32d42ad8da193e6da285f09e6452feabda (CNA: Linux)

- https://git.kernel.org/stable/c/66aefc277ebb796ec285d550305535dc3fc0179f (CNA: Linux)

- https://git.kernel.org/stable/c/1357fb32d42ad8da193e6da285f09e6452feabda (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/18d4f86816592586b38513543b5e1f9553bc271f (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/255fb7b0cdc947b1c01929c7f133281342a3a6b5 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/4567ce79fe2f84c3dcc3a91b22a377cf482d33ad (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/66aefc277ebb796ec285d550305535dc3fc0179f (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/6c01f0439098f00a64b246dc27479602201382f7 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/fbc1bdede66d0f2cde83b75d6524ce1a815bb69f (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-72086; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72086; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-72086; retrieved 2026-11-06; source updated Not reported

Revision: b010ebc6f844b07c6eb300c2fb726cc6dc4c48772f415b0bf50d55c356f80a25

Canonical: https://y2.dev/cve/CVE-2026-72086

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