NVD / CVE Program· CNA Linux

CVE-2026-53198: ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL

Noroxi assessment

Priority: Monitor (action score 35/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.44% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Linux Linux 0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd, 14d2eee0193ac3cd1bf3d014373449f0b8d35d6d, 2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694.

Low priority for now. Upgrade to Linux Linux 0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd, 14d2eee0193ac3cd1bf3d014373449f0b8d35d6d, 2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free of a deferred file_lock on double SMB2_CANCEL A deferred byte-range lock (an SMB2_LOCK that blocks) registers an async work on conn->async_requests via setup_async_work(), with cancel_fn = smb2_remove_blocked_lock and cancel_argv[0] pointing at the struct file_lock. When the request is cancelled, the worker frees the file_lock with locks_free_lock() and takes the cancelled early-exit, which "goto out"s and never reaches release_async_work() -- the only site that unlinks the work from conn->async_requests and clears cancel_fn/cancel_argv. The work therefore stays matchable on async_requests with a live cancel_fn pointing at the freed file_lock, until connection teardown finally runs release_async_work(). smb2_cancel() fires cancel_fn unconditionally with no state guard, so a second SMB2_CANCEL for the same AsyncId, arriving in that window, re-runs smb2_remove_blocked_lock() on the freed file_lock -- a slab use-after-free: BUG: KASAN: slab-use-after-free in __locks_delete_block __locks_delete_block locks_delete_block ksmbd_vfs_posix_lock_unblock smb2_remove_blocked_lock smb2_cancel <- 2nd SMB2_CANCEL fires cancel_fn handle_ksmbd_work Allocated by ...: locks_alloc_lock <- smb2_lock Freed by ...: locks_free_lock <- smb2_lock (cancelled branch) ... cache file_lock_cache of size 192 Reproduced on mainline with KASAN by an authenticated SMB client. Skip a work whose state is already KSMBD_WORK_CANCELLED so its cancel callback cannot be fired a second time.

HighCVSS 8.8 · v3.1—No exploit Fix available

Memory safety

Published: Jun 25, 2026
Updated: Oct 15, 2026
EPSS: 0.4% · 38th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 35 / 40 · 8.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.4%

CNA vs NVD score

NVD: —
CNA · Linux: 8.8; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

linux linux kernel5.15 and later · before 6.1.176
linux linux kernel6.2 and later · before 6.6.143
linux linux kernel6.7 and later · before 6.12.94
linux linux kernel6.13 and later · before 6.18.36
linux linux kernel6.19 and later · before 7.0.13
linux linux kernel7.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

Linux Linux
- 5.15affected
- e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before b7063c7426ea5a4d15e01b60538718765392f49daffected · git
- e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before 0da2e073f9cbf4985a0fd9acb71bc5ff599f8afdaffected · git
- e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before 89ae9df09d2c1fb4a4eb495c113a7ce1dca34147affected · git
- e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before 14d2eee0193ac3cd1bf3d014373449f0b8d35d6daffected · git
- e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before 2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694affected · git
- e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before f580d27e8928828693df44ba2db0fffdbe11dfeaaffected · git
- before 5.15not affected · semver
- 6.1.176 and later · up to and including 6.1.*not affected · semver
- 6.6.143 and later · up to and including 6.6.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	linux	before 6.1.176-1	6.1.176-1
Debian:13	linux	before 6.12.94-1	6.12.94-1
Debian:14	linux	before 7.0.13-1	7.0.13-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
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CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
89Now
CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
85Now

Published before and after this one in the same product

← EarlierCVE-2026-53195Jun 25, 2026 · USB: serial: io_ti: fix heap overflow in build_i2c_fw_hdr()
31Monitor
← EarlierCVE-2026-53196Jun 25, 2026 · USB: serial: io_ti: fix heap overflow in get_manuf_info()
27Monitor
Later →CVE-2026-53199Jun 25, 2026 · hv_netvsc: use kmap_local_page in netvsc_copy_to_send_buf
30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Linux Linux	0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd	Vendor (CNA)
Linux Linux	14d2eee0193ac3cd1bf3d014373449f0b8d35d6d	Vendor (CNA)
Linux Linux	2b2eda2821cff1d1b5a423b6ee7d8fc6fbc8e694	Vendor (CNA)
Linux Linux	89ae9df09d2c1fb4a4eb495c113a7ce1dca34147	Vendor (CNA)
Linux Linux	b7063c7426ea5a4d15e01b60538718765392f49d	Vendor (CNA)
Linux Linux	f580d27e8928828693df44ba2db0fffdbe11dfea	Vendor (CNA)
debian:linux	6.1.176-1 · Debian:12	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:09 PM UTC

For records you follow, these changes also arrive as notifications. →

References

git.kernel.org/stable/c/0da2e073f9cbf4985a0fd9acb71bc5ff599f8afd

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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