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NVD / CVE Program· CNA Linux

CVE-2026-53390: ksmbd: fix out-of-bounds read in smb_check_perm_dacl()

Noroxi assessment

Priority: Monitor (action score 32/100)

  • 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. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b, 36599894fa8536fefdf1e296c0af71b8b7226859, 5.15.212.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1ef06004ed4bd6d3ed8c840d9d1a376b66d4935b, 36599894fa8536fefdf1e296c0af71b8b7226859, 5.15.212 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 out-of-bounds read in smb_check_perm_dacl() The permission-check ACE walk in smb_check_perm_dacl() validates the ACE header size and caps sid.num_subauth at SID_MAX_SUB_AUTHORITIES, but it never checks that ace->size is actually large enough to contain num_subauth sub-authorities before compare_sids() dereferences them. CIFS_SID_BASE_SIZE covers the SID header up to but excluding the sub_auth[] array, and offsetof(struct smb_ace, sid) is the ACE header, so the existing guards only guarantee the 8-byte SID base, i.e. zero sub-authorities. compare_sids() then reads ace->sid.sub_auth[i] for i < min(local_sid->num_subauth, ace->sid.num_subauth). The local comparison SIDs (sid_everyone, sid_unix_NFS_mode, and the id_to_sid() result) always have at least one sub-authority, and an attacker controls the ACE revision and authority bytes (which lie within the in-bounds SID base), so they can match one of those SIDs and force the sub_auth read. A crafted ACE with size == 16 and num_subauth >= 1 placed at the tail of the security descriptor therefore causes a heap out-of-bounds read of up to SID_MAX_SUB_AUTHORITIES * sizeof(__le32) bytes past the pntsd allocation. The security descriptor is loaded by ksmbd_vfs_get_sd_xattr() into a buffer sized exactly to the on-disk data (kzalloc(sd_size) in ndr_decode_v4_ntacl()), so the read lands past the allocation. The malformed descriptor can be stored verbatim via SMB2_SET_INFO (the DACL is not normalised before being written to the security.NTACL xattr) and the read fires on a subsequent SMB2_CREATE access check, making this reachable by an authenticated client on a share that uses ACL xattrs. Add the missing num_subauth-versus-ace_size check, mirroring the identical guards already present in the sibling parsers parse_dacl() and smb_inherit_dacl().

HighCVSS 8.1 · v3.1—No exploit Fix available
Published
Jul 19, 2026
Updated
Aug 17, 2026
EPSS
0.4% · 40th percentile

Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
32 / 40 · 8.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CNA vs NVD score

NVD
—
CNA · Linux
8.1
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

  • 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 kernel5.15.210 and later · before 5.15.212
  • linux linux kernel6.6.140 and later · before 6.6.144
  • linux linux kernel6.12.84 and later · before 6.12.95
  • linux linux kernel6.18.25 and later · before 6.18.38
  • linux linux kernel7.0.2 and later · before 7.1.3
  • linux linux kernel6.1.176

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

    • 151b1799861fde38087c08f613abc2843ef597b0, 7.1affected
    • 282cbbb476b9f35793452bc461934af4c7eca169 and later · before c7488c85fd822959e9b5c22fbd9e7c8a21caf5e0affected · git
    • f20adc4ef7428bc485ee83fd1a592252fb87718b and later · before 988c93d3bba066d8669143e6ec30bb2be9608d53affected · git
    • 325d4ac11f526cb8964cff14548ccf02d8c756d8 and later · before 36599894fa8536fefdf1e296c0af71b8b7226859affected · git
    • 95e5aa3c3261da8c95b27d7aecf8ee39b9f86a4c and later · before d5c81a095c86fe507c032d08f3a8cfc518444927affected · git
    • 90089584b2e25c4510b7b987387b4405f0673ece and later · before 7627ff8c4f9919f14de562b0160ab4ec9d80b1f7affected · git
    • d07b26f39246a82399661936dd0c853983cfade7 and later · before e36e35660adb9b8ef1435ac359151dda5f094c55affected · git
    • d07b26f39246a82399661936dd0c853983cfade7 and later · before 1ef06004ed4bd6d3ed8c840d9d1a376b66d4935baffected · git
    • 5.15.210 and later · before 5.15.212affected · semver
    • 6.1.176 and later · before 6.1.177affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.177-16.1.177-1
Debian:13linuxbefore 6.12.95-16.12.95-1
Debian:14linuxbefore 7.1.3-17.1.3-1
openSUSE:Tumbleweedkernel-sourcebefore 7.1.4-1.17.1.4-1.1

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-2026-53387Jul 19, 2026 · iio: light: veml6075: add bounds check to veml6075_it_ms index
    28Monitor
  • ← EarlierCVE-2026-53389Jul 19, 2026 · net/tcp-ao: fix use-after-free of key in del_async path
    31Monitor
  • Later →CVE-2026-53393Jul 19, 2026 · nfsd: reset write verifier on deferred writeback errors
    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 Linux1ef06004ed4bd6d3ed8c840d9d1a376b66d4935bVendor (CNA)
Linux Linux36599894fa8536fefdf1e296c0af71b8b7226859Vendor (CNA)
Linux Linux5.15.212Vendor (CNA)
Linux Linux6.1.177Vendor (CNA)
Linux Linux6.12.95Vendor (CNA)
Linux Linux6.18.38Vendor (CNA)
Linux Linux6.6.144Vendor (CNA)
Linux Linux7.1Vendor (CNA)
Linux Linux7627ff8c4f9919f14de562b0160ab4ec9d80b1f7Vendor (CNA)
Linux Linux988c93d3bba066d8669143e6ec30bb2be9608d53Vendor (CNA)
Linux Linuxc7488c85fd822959e9b5c22fbd9e7c8a21caf5e0Vendor (CNA)
Linux Linuxd5c81a095c86fe507c032d08f3a8cfc518444927Vendor (CNA)
Linux Linuxe36e35660adb9b8ef1435ac359151dda5f094c55Vendor (CNA)
debian:linux6.1.177-1 · Debian:12Package registry (OSV)
opensuse:kernel-source7.1.4-1.1 · openSUSE:TumbleweedPackage 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

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
none
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
None
Availability impact
High

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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

ATT&CK techniques

—

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