NVD / CVE Program· CNA Linux

CVE-2026-31718: ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger

Noroxi assessment

Priority: Monitor (action score 39/100)

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: 0.35% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Linux Linux 0000a7780e0e446a28a273572f6ea8f7f582f694, 235e32320a470fcd3998fb3774f2290a0eb302a1, 3d6682726c2d3a46d31dae88b8166786b09b03ad.

Low priority for now. Upgrade to Linux Linux 0000a7780e0e446a28a273572f6ea8f7f582f694, 235e32320a470fcd3998fb3774f2290a0eb302a1, 3d6682726c2d3a46d31dae88b8166786b09b03ad 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 in __ksmbd_close_fd() via durable scavenger When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list. Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did: spin_lock(&fp->conn->llist_lock); This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect(). The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out. To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().

CriticalCVSS 9.8 · v3.1—No exploit Fix available

BDU:2026-10729

Published: May 1, 2026
Updated: Aug 5, 2026
EPSS: 0.3% · 29th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.3%

CNA vs NVD score

NVD: —
CNA · Linux: 9.8; 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.

Get told when this record changes

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 kernel6.6.32 and later · before 6.7
linux linux kernel6.9 and later · before 6.12.84
linux linux kernel6.13 and later · before 6.18.25
linux linux kernel6.19 and later · before 7.0.2
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
- 6.9affected
- 8df4bcdb0a4232192b2445256c39b787d58ef14d and later · before 0000a7780e0e446a28a273572f6ea8f7f582f694affected · git
- c8efcc786146a951091588e5fa7e3c754850cb3c and later · before e33c65f011980b4ad4abfd93585ec2079856368faffected · git
- c8efcc786146a951091588e5fa7e3c754850cb3c and later · before 3d6682726c2d3a46d31dae88b8166786b09b03adaffected · git
- c8efcc786146a951091588e5fa7e3c754850cb3c and later · before b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9affected · git
- c8efcc786146a951091588e5fa7e3c754850cb3c and later · before 235e32320a470fcd3998fb3774f2290a0eb302a1affected · git
- 6.6.32 and later · before 6.6.140affected · semver
- before 6.9not affected · semver
- 6.6.140 and later · up to and including 6.6.*not affected · semver
- 6.12.84 and later · up to and including 6.12.*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:13	linux	before 6.12.85-1	6.12.85-1
Debian:14	linux	before 7.0.3-1	7.0.3-1

Same product

linux: all records

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Published before and after this one in the same product

← EarlierCVE-2026-31716May 1, 2026 · fs/ntfs3: validate rec->used in journal-replay file record check
31Monitor
← EarlierCVE-2026-31717May 1, 2026 · ksmbd: validate owner of durable handle on reconnect
35Monitor
Later →CVE-2026-31720May 1, 2026 · usb: gadget: f_uac1_legacy: validate control request size
31Monitor

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	0000a7780e0e446a28a273572f6ea8f7f582f694	Vendor (CNA)
Linux Linux	235e32320a470fcd3998fb3774f2290a0eb302a1	Vendor (CNA)
Linux Linux	3d6682726c2d3a46d31dae88b8166786b09b03ad	Vendor (CNA)
Linux Linux	6.6.140	Vendor (CNA)
Linux Linux	b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9	Vendor (CNA)
Linux Linux	e33c65f011980b4ad4abfd93585ec2079856368f	Vendor (CNA)
debian:linux	6.12.85-1 · Debian:13	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.
No account or password is required.
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: None
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:N/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, 10:11 PM UTC

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

References

git.kernel.org/stable/c/0000a7780e0e446a28a273572f6ea8f7f582f694

Show all references (4 more)

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

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