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Response snapshot Oct 26, 2026, 21:47 UTC

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VulnerabilityCVE-2026-99083

Linux kernel: ksmbd: fix heap out-of-bounds write in krb5_authenticate()

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.

At a glance

Exploited
Not known
Severity
8.8 High (CVSS 3.1)
Chance of exploitation
0.4% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-99083 (opens a new tab)

What happened

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.

Continue reading

Fix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len, ensuring it accurately reflects physical remaining buffer space.

Scores and how they were measured

CVSS base severity

8.8

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.4%

Scored Percentile 34.8%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-99083 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-99083, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 26). Linux kernel: ksmbd: fix heap out-of-bounds write in krb5_authenticate() (CVE-2026-99083). https://kevwire.com/record/CVE-2026-99083

MLA

"Linux kernel: ksmbd: fix heap out-of-bounds write in krb5_authenticate() (CVE-2026-99083)." KEVWire, 26 Oct. 2026, kevwire.com/record/CVE-2026-99083.

Chicago

KEVWire. "Linux kernel: ksmbd: fix heap out-of-bounds write in krb5_authenticate() (CVE-2026-99083)." Last modified October 26, 2026. https://kevwire.com/record/CVE-2026-99083.

Evidence summary (plain text)

Linux kernel: ksmbd: fix heap out-of-bounds write in krb5_authenticate() (Oct 23, 2026).
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.
CVSS 8.8 (version 3.1; evidence as of Oct 26, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-99083).
EPSS 0.4% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-99083&date=2026-10-26).
Sources:
NVD CVE-2026-99083: https://nvd.nist.gov/vuln/detail/CVE-2026-99083
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?pubStartDate=2026-10-12T13:35:55.142Z&pubEndDate=2026-10-26T13:35:55.142Z&resultsPerPage=500&startIndex=9000
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-99083&date=2026-10-26
Record ID: CVE-2026-99083.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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