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NVD / CVE Program· CNA Linux

CVE-2025-21994: ksmbd: fix incorrect validation for num_aces field of smb_acl

Noroxi assessment

Priority: Monitor (action score 22/100)

  • 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: 0.30% (FIRST EPSS).
  • Someone with local access to the system 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 1b8b67f3c5e5169535e26efedd3e422172e2db64, 9c4e202abff45f8eac17989e549fc7a75095f675, a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd.
  • Severity is disputed: the assigning authority (CNA) scores it 7.6, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 1b8b67f3c5e5169535e26efedd3e422172e2db64, 9c4e202abff45f8eac17989e549fc7a75095f675, a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd 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 incorrect validation for num_aces field of smb_acl parse_dcal() validate num_aces to allocate posix_ace_state_array. if (num_aces > ULONG_MAX / sizeof(struct smb_ace *)) It is an incorrect validation that we can create an array of size ULONG_MAX. smb_acl has ->size field to calculate actual number of aces in request buffer size. Use this to check invalid num_aces.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Apr 2, 2025
Updated
Aug 5, 2026
EPSS
0.3% · 23th percentile
CWE
—

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CNA vs NVD score

NVD
5.5
CNA · Linux
7.6
2.1 point gap

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

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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When you'll hear from us

  • when it enters CISA KEV
  • 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?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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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 and later · before 5.15.180
  • linux linux kernel5.16 and later · before 6.1.132
  • linux linux kernel6.2 and later · before 6.6.85
  • linux linux kernel6.7 and later · before 6.12.21
  • linux linux kernel6.13 and later · before 6.13.9
  • linux linux kernel6.14

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
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before c3a3484d9d31b27a3db0fab91fcf191132d65236affected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before 9c4e202abff45f8eac17989e549fc7a75095f675affected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before d0f87370622a853b57e851f7d5a5452b72300f19affected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before a4cb17797a5d241f1e509cb5b46ed95a80c2f5fdaffected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before f6a6721802ac2f12f4c1bbe839a4c229b61866f2affected · git
    • 0626e6641f6b467447c81dd7678a69c66f7746cf and later · before 1b8b67f3c5e5169535e26efedd3e422172e2db64affected · git
    • before 5.15not affected · semver
    • 5.15.180 and later · up to and including 5.15.*not affected · semver
    • 6.1.132 and later · up to and including 6.1.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.133-16.1.133-1
Debian:13linuxbefore 6.12.21-16.12.21-1

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-2025-21992Apr 2, 2025 · HID: ignore non-functional sensor in HP 5MP Camera
    22Monitor
  • ← EarlierCVE-2025-21993Apr 2, 2025 · iscsi_ibft: Fix UBSAN shift-out-of-bounds warning in ibft_attr_show_nic()
    28Monitor
  • Later →CVE-2025-21995Apr 3, 2025 · drm/sched: Fix fence reference count leak
    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 Linux1b8b67f3c5e5169535e26efedd3e422172e2db64Vendor (CNA)
Linux Linux9c4e202abff45f8eac17989e549fc7a75095f675Vendor (CNA)
Linux Linuxa4cb17797a5d241f1e509cb5b46ed95a80c2f5fdVendor (CNA)
Linux Linuxc3a3484d9d31b27a3db0fab91fcf191132d65236Vendor (CNA)
Linux Linuxd0f87370622a853b57e851f7d5a5452b72300f19Vendor (CNA)
Linux Linuxf6a6721802ac2f12f4c1bbe839a4c229b61866f2Vendor (CNA)
debian:linux6.1.133-1 · 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

  • Someone with local access to the system 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
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-primary

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 (6 more)

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

All records