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TI-2026-79876 Aliases CVE-2026-99083GHSA-2j87-48p3-j5xw

Heap out-of-bounds write in Linux kernel ksmbd krb5_authenticate()

Priority LOW 38Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

The Linux kernel ksmbd SMB server is affected in versions from 5.15.145 before 5.15.224, from 6.1.40 before 6.1.191, and from 6.4.5 before 6.5. A buffer size calculation in krb5_authenticate() ignores the offset of earlier responses in a compounded SMB2 request, so a length check passes when it should fail. This lets a memcpy() write past the end of the response buffer into adjacent kernel heap memory. A remote attacker with low privileges can use this to affect confidentiality, integrity and availability.

Written with Claude Haiku 5.5 from the sources below · 2026-10-30

Description from the CNA

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.

Why it matters now

EPSS 0.00445 38th percentileScored 2026-11-07
Fix Fixed Linux (Linux): 5.15.224, 6.1.191, 6.5 +5

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.15.145 to before 5.15.224; 6.1.40 to before 6.1.191; 6.4.5 to before 6.55.15.224, 6.1.191, 6.5Patch availableCNA
LinuxLinux6.5 and later5.15.224, 6.1.191, 6.6.160, 6.12.114, 6.18.58, 7.2.12, 7.3Patch availableCNA
  • Linux VendorLinux Affected 5.15.145 to before 5.15.224; 6.1.40 to before 6.1.191; 6.4.5 to before 6.5 Fixed in 5.15.224, 6.1.191, 6.5 Patch available CNA
  • Linux VendorLinux Affected 6.5 and later Fixed in 5.15.224, 6.1.191, 6.6.160, 6.12.114, 6.18.58, 7.2.12, 7.3 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*——Linux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions — — ·Linux

Remediation

Update the Linux kernel to 5.15.224, 6.1.191, 6.5, 6.6.160, 6.12.114, 6.18.58, 7.2.12 or 7.3, depending on the branch in use.

Written with Claude Haiku 5.5 from the sources below · 2026-10-30

  • Fix · CNA Linux (Linux) Fixed in 5.15.224, 6.1.191, 6.5
  • Fix · CNA Linux (Linux) Fixed in 5.15.224, 6.1.191, 6.6.160, 6.12.114, 6.18.58, 7.2.12, 7.3

Vendor assessments

Red Hat

Red Hat rating: Critical. Red Hat's page for this CVE →

Not affected: 7 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat OpenShift Container Platform 4
  • Red Hat OpenShift Container Platform 5

Timeline

  1. 2026-10-23 Threatist record created from CVE-2026-99083
  2. 2026-10-23 Alias added: GHSA-2j87-48p3-j5xw
  3. 2026-10-24 CVSS score added · CNA
  4. 2026-10-24 Priority changed: LOW → MEDIUM
  5. 2026-10-24 Priority changed: MEDIUM → LOW
  6. 2026-10-26 Fix available: Linux/Linux@0, Linux/[email protected], Linux/[email protected] +1 · CNA
  7. 2026-10-26 Affected versions changed · Red Hat
  8. 2026-10-26 CVSS score added · Red Hat
  9. 2026-10-30 Fix available: Linux/Linux@1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ff, Linux/[email protected], Linux/[email protected] +1 · CNA
  10. 2026-10-30 2 new references · CNA
  11. 2026-10-30 Affected versions changed · Red Hat

References

Other 7

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2021-02452 Incorrect authorization in Ubuntu linux kernel KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
See all 21727 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences