CVE-2026-72085: Linux Vulnerability (CVSS 9.3)

Description

In the Linux kernel, the following vulnerability has been resolved: scsi: xen: scsiback: Free unsubmitted command instead of double-putting it scsiback_get_pend_req() obtains a command tag and returns a vscsibk_pend whose embedded se_cmd has only been memset to 0, so its cmd_kref is 0; the se_cmd is initialised (kref_init() via target_init_cmd()) only later, in scsiback_cmd_exec(), on the successful VSCSIIF_ACT_SCSI_CDB path. The two error paths in scsiback_do_cmd_fn() taken before the command is submitted -- a failed scsiback_gnttab_data_map() and an unknown ring_req.act -- call transport_generic_free_cmd(&pending_req->se_cmd, 0), which kref_put()s a refcount of 0. That underflows it ("refcount_t: underflow; use-after-free") and, as the release function is not run, leaks the command tag. Impact: a pvSCSI guest can leak every command tag of a LUN's session, stopping the LUN, by submitting requests with a bad grant reference or an unknown request type; under panic_on_warn the refcount underflow panics the host. Add a helper that just returns the tag with target_free_tag() and sends the error response. It frees the tag while the v2p reference still pins the session, and snapshots the response fields beforehand because freeing the tag can let another ring reuse the pending_req slot.

Metrics

CVSS 3.1

9.3/10

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.21%

10.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

Vendor	Product	Versions
Linux	Linux	>= 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, < 9c0f6894982b1f13bda220707497b25ac9c95bdb; >= 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, < a13b789497a7fdd27d4d63f5c69d23db706ef0fe; >= 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, < fa588f28401102652068c4cc75e135507f4b5106; >= 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, < fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45; >= 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, < f1516c56ac540da1769f264c3cfefe4499548a5d; >= 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, < 1e97c404e44991fb087c38ccd7414f2d326f9b74; >= 2dbcdf33dbf61f44b29adb52338282c3d7840d0e, < ca978f8a93d4d36841839bf2847d29b88c2591d6
Linux	Linux	4.6

References

Timeline

Published: Aug 15, 2026
Last Modified: Aug 17, 2026
Status: Received

Frequently Asked Questions

What is CVE-2026-72085?

In the Linux kernel, the following vulnerability has been resolved: scsi: xen: scsiback: Free unsubmitted command instead of double-putting it scsiback_get_pend_req() obtains a command tag and returns a vscsibk_pend whose embedded se_cmd has only been memset to 0, so its cmd_kref is 0; the se_cmd is initialised (kref_init() via target_init_cmd()) only later, in scsiback_cmd_exec(), on the successful VSCSIIF_ACT_SCSI_CDB path. The two error paths in scsiback_do_cmd_fn() taken before the command is submitted -- a failed scsiback_gnttab_data_map() and an unknown ring_req.act -- call transport_generic_free_cmd(&pending_req->se_cmd, 0), which kref_put()s a refcount of 0. That underflows it ("refcount_t: underflow; use-after-free") and, as the release function is not run, leaks the command tag. Impact: a pvSCSI guest can leak every command tag of a LUN's session, stopping the LUN, by submitting requests with a bad grant reference or an unknown request type; under panic_on_warn the refcount underflow panics the host. Add a helper that just returns the tag with target_free_tag() and sends the error response. It frees the tag while the v2p reference still pins the session, and snapshots the response fields beforehand because freeing the tag can let another ring reuse the pending_req slot.

How severe is CVE-2026-72085?

CVE-2026-72085 has a CVSS score of 9.3/10 (CRITICAL severity). The EPSS model estimates a 0.21% probability of exploitation in the next 30 days.

How do I fix CVE-2026-72085?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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