Linux: Use After Free
CVE-2026-72085 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.3 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists versions 9c0f6894982b1f13bda220707497b25ac9c95bdb, a13b789497a7fdd27d4d63f5c69d23db706ef0fe, fa588f28401102652068c4cc75e135507f4b5106 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.18% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Linux to 9c0f6894982b1f13bda220707497b25ac9c95bdb or a13b789497a7fdd27d4d63f5c69d23db706ef0fe or fa588f28401102652068c4cc75e135507f4b5106 or fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 2dbcdf33dbf61f44b29adb52338282c3d7840d0e up to, but not including, 9c0f6894982b1f13bda220707497b25ac9c95bdb; 2dbcdf33dbf61f44b29adb52338282c3d7840d0e up to, but not including, a13b789497a7fdd27d4d63f5c69d23db706ef0fe; 2dbcdf33dbf61f44b29adb52338282c3d7840d0e up to, but not including, fa588f28401102652068c4cc75e135507f4b5106; 2dbcdf33dbf61f44b29adb52338282c3d7840d0e up to, but not including, fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45; 2dbcdf33dbf61f44b29adb52338282c3d7840d0e up to, but not including, f1516c56ac540da1769f264c3cfefe4499548a5d; 2dbcdf33dbf61f44b29adb52338282c3d7840d0e up to, but not including, 1e97c404e44991fb087c38ccd7414f2d326f9b74; 2dbcdf33dbf61f44b29adb52338282c3d7840d0e up to, but not including, ca978f8a93d4d36841839bf2847d29b88c2591d6; 4.6 | 9c0f6894982b1f13bda220707497b25ac9c95bdb, a13b789497a7fdd27d4d63f5c69d23db706ef0fe, fa588f28401102652068c4cc75e135507f4b5106, fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45, f1516c56ac540da1769f264c3cfefe4499548a5d, 1e97c404e44991fb087c38ccd7414f2d326f9b74 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by CNA.
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- git.kernel.org/stable/c/1e97c404e44991fb087c38ccd7414f2d326f9b74
- git.kernel.org/stable/c/9c0f6894982b1f13bda220707497b25ac9c95bdb
- git.kernel.org/stable/c/a13b789497a7fdd27d4d63f5c69d23db706ef0fe
- git.kernel.org/stable/c/ca978f8a93d4d36841839bf2847d29b88c2591d6
- git.kernel.org/stable/c/f1516c56ac540da1769f264c3cfefe4499548a5d
- git.kernel.org/stable/c/fa588f28401102652068c4cc75e135507f4b5106
- git.kernel.org/stable/c/fcd64d4d97af5d9736f31040f8ed8cd4c17e4c45
Recent Use After Free vulnerabilities
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 9.8 Critical severity
- 8.8 High severity
- 7.8 High severity
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