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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-99083: ksmbd: fix heap out-of-bounds write in krb5_authenticate()

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: 0.40% (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 1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ff, 23a0be6a84a38ac169eeab49017934e8e27c65f0, 4722d06b2907585074252061b1024a696c1cfc23; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes.

Low priority for now. Upgrade to Linux Linux 1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ff, 23a0be6a84a38ac169eeab49017934e8e27c65f0, 4722d06b2907585074252061b1024a696c1cfc23; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes 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 heap out-of-bounds write in krb5_authenticate() In krb5_authenticate(), out_len is calculated to determine available headroom in response_buf for the incoming Kerberos AP-REP token. However, when SMB2_SESSION_SETUP is processed as a non-first element of a compounded SMB2 request, the calculation omits work->next_smb2_rsp_hdr_off. This causes out_len to overstate remaining buffer headroom by the cumulative size of prior responses in the compound chain. Consequently, the length check in ksmbd_krb5_authenticate() (*out_len <= resp->spnego_blob_len) passes erroneously, allowing memcpy() to write the AP-REP blob past the end of response_buf into adjacent kernel heap memory. Fix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len, ensuring it accurately reflects physical remaining buffer space.

HighCVSS 8.8 · v3.1—No exploit Fix available
Published
Oct 23, 2026
Updated
Oct 30, 2026
EPSS
0.4% · 35th percentile
CWE
—

Report tools

JSON

Action score

35

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

If any of these changes, we'll tell you in the daily email digest.

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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.

—

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

    • 2ba03cecb12ac7ac9e0170e251543c56832d9959, 6.5affected
    • 676392184785ace61e939831e7ca44a03d438c3b and later · before a07dfb33112a42437f9d2d0bfd35c68575257381affected · git
    • ef572ffa8eb44111eed2925fbb2adca78bdcbf61 and later · before 1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ffaffected · git
    • 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 and later · before 59c6dcc5dd9dafe764ca0d40525933b2be69b059affected · git
    • 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 and later · before 80af1bde97d5a85ad6f2c40ca894ccc8fa75a27aaffected · git
    • 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 and later · before 517404e157395d0f8da125ca956c566895dfcd06affected · git
    • 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 and later · before 4722d06b2907585074252061b1024a696c1cfc23affected · git
    • 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 and later · before 23a0be6a84a38ac169eeab49017934e8e27c65f0affected · git
    • 5.15.145 and later · before 5.15.224affected · semver
    • 6.1.40 and later · before 6.1.191affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:14linuxbefore 7.2.12-17.2.12-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-99081Oct 23, 2026 · bnxt_en: fix DMA mapping length for padded small packets
    30Monitor
  • ← EarlierCVE-2026-99082Oct 23, 2026 · KVM: x86: Use active memslots for the per-vCPU MMIO cache
    35Monitor
  • Later →CVE-2026-99084Oct 23, 2026 · readdir: take no inode lock on an immutable directory
    0Monitor

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 Linux1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ffVendor (CNA)
Linux Linux23a0be6a84a38ac169eeab49017934e8e27c65f0Vendor (CNA)
Linux Linux4722d06b2907585074252061b1024a696c1cfc23Vendor (CNA)
Linux Linux5.15.224Vendor (CNA)
Linux Linux517404e157395d0f8da125ca956c566895dfcd06Vendor (CNA)
Linux Linux59c6dcc5dd9dafe764ca0d40525933b2be69b059Vendor (CNA)
Linux Linux6.1.191Vendor (CNA)
Linux Linux6.5Vendor (CNA)
Linux Linux80af1bde97d5a85ad6f2c40ca894ccc8fa75a27aVendor (CNA)
Linux Linuxa07dfb33112a42437f9d2d0bfd35c68575257381Vendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
debian:linux7.2.12-1 · Debian:14Package 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.

  1. Published
  2. Fix recordedsame day
  3. TodayOct 31, 2026+8 d
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).

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)

—

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/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. CVSS— → 8.8
  2. Severity— → high
  3. Exploit maturity— → none
  4. Fix✗ → ✓

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

References

Show all references (4 more)

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

All records