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NVD / CVE Program· CNA Linux

CVE-2026-31477: ksmbd: fix memory leaks and NULL deref in smb2_lock()

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 0.47% (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 309b44ed684496ed3f9c5715d10b899338623512, 3cdacd11b41569ce75b3162142240f2355e04900, 91aeaa7256006d79a37298f5a1df23325db91599.

Low priority for now. Upgrade to Linux Linux 309b44ed684496ed3f9c5715d10b899338623512, 3cdacd11b41569ce75b3162142240f2355e04900, 91aeaa7256006d79a37298f5a1df23325db91599 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 memory leaks and NULL deref in smb2_lock() smb2_lock() has three error handling issues after list_del() detaches smb_lock from lock_list at no_check_cl: 1) If vfs_lock_file() returns an unexpected error in the non-UNLOCK path, goto out leaks smb_lock and its flock because the out: handler only iterates lock_list and rollback_list, neither of which contains the detached smb_lock. 2) If vfs_lock_file() returns -ENOENT in the UNLOCK path, goto out leaks smb_lock and flock for the same reason. The error code returned to the dispatcher is also stale. 3) In the rollback path, smb_flock_init() can return NULL on allocation failure. The result is dereferenced unconditionally, causing a kernel NULL pointer dereference. Add a NULL check to prevent the crash and clean up the bookkeeping; the VFS lock itself cannot be rolled back without the allocation and will be released at file or connection teardown. Fix cases 1 and 2 by hoisting the locks_free_lock()/kfree() to before the if(!rc) check in the UNLOCK branch so all exit paths share one free site, and by freeing smb_lock and flock before goto out in the non-UNLOCK branch. Propagate the correct error code in both cases. Fix case 3 by wrapping the VFS unlock in an if(rlock) guard and adding a NULL check for locks_free_lock(rlock) in the shared cleanup. Found via call-graph analysis using sqry.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Apr 22, 2026
Updated
Aug 5, 2026
EPSS
0.4% · 41th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CNA vs NVD score

NVD
—
CNA · Linux
7.5
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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When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
linuxlinux kernel

Affected versions

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

  • linux linux kernel5.15.1 and later · before 6.1.168
  • linux linux kernel6.2 and later · before 6.6.131
  • linux linux kernel6.7 and later · before 6.12.80
  • linux linux kernel6.13 and later · before 6.18.21
  • linux linux kernel6.19 and later · before 6.19.11
  • linux linux kernel5.15
  • linux linux kernel7.0

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 cdac6f7e7e428dc70e3b5898ac6999a72ed13993affected · git
    • e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before c9b95ef6f5039f19e46c3a521a4fe1752d91dfe9affected · git
    • e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before 91aeaa7256006d79a37298f5a1df23325db91599affected · git
    • e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before 3cdacd11b41569ce75b3162142240f2355e04900affected · git
    • e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before aab42f0795620cf0d3955a520f571f697d0f9a2aaffected · git
    • e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and later · before 309b44ed684496ed3f9c5715d10b899338623512affected · git
    • before 5.15not affected · semver
    • 6.1.168 and later · up to and including 6.1.*not affected · semver
    • 6.6.131 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.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.11-16.19.11-1

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
    90Now
  • 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-2026-31475Apr 22, 2026 · ASoC: sma1307: fix double free of devm_kzalloc() memory
    31Monitor
  • ← EarlierCVE-2026-31476Apr 22, 2026 · ksmbd: do not expire session on binding failure
    32Monitor
  • Later →CVE-2026-31480Apr 22, 2026 · tracing: Fix potential deadlock in cpu hotplug with osnoise
    22Monitor

Remediation

Which version to upgrade to

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

Product / packageFixed versionSource
Linux Linux309b44ed684496ed3f9c5715d10b899338623512Vendor (CNA)
Linux Linux3cdacd11b41569ce75b3162142240f2355e04900Vendor (CNA)
Linux Linux91aeaa7256006d79a37298f5a1df23325db91599Vendor (CNA)
Linux Linuxaab42f0795620cf0d3955a520f571f697d0f9a2aVendor (CNA)
Linux Linuxc9b95ef6f5039f19e46c3a521a4fe1752d91dfe9Vendor (CNA)
Linux Linuxcdac6f7e7e428dc70e3b5898ac6999a72ed13993Vendor (CNA)
debian:linux6.1.170-1 · Debian:12Package 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
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

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

nvd-secondary

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

  1. Fix✗ → ✓

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

References

Show all references (5 more)

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

All records