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Full vulnerability report · 2025
CVE-2023-54203High confidence

ksmbd: fix slab-out-of-bounds in init_smb2_rsp_hdr

Linux · Linux

9.1CriticalCVSS 3.1
Recommended action
Within 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Fix not verified
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.55% for the current model date.

Compensating controls

  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Linux Linux and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

13 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcelinuxNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian bookwormbookworm · sourcelinuxNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian forkyforky · sourcelinuxNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Debian sidsid · sourcelinuxNot affectedDebian marks this release not affected (fixed-version marker 0).Not published in this feedDebian Security Tracker ↗Source updated 6 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-azure-6.11Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-gcp-6.11Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-hwe-6.11Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-lowlatency-hwe-6.11Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-nvidia-6.11Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-oem-6.11Affected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-raspi-realtimeAffected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-realtimeAffected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivelinux-riscvAffected, no fix publishedCanonical OVAL identifies this running kernel flavour as affected and does not publish a fixed package version in this definition.Not published in this feedCanonical Ubuntu Security ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2023-54203 · CSAF 2.0 · revision 3 · finalRed Hat Product Securitykernel: Linux kernel ksmbd: Slab-out-of-bounds vulnerability allows information disclosure and denial of service
274 known not affected

The vendor explicitly states that these products are not affected by this CVE.

  • kernel as a component of Red Hat Enterprise Linux 10
  • kernel-64k as a component of Red Hat Enterprise Linux 10
  • kernel-64k-core as a component of Red Hat Enterprise Linux 10
  • kernel-64k-debug as a component of Red Hat Enterprise Linux 10
  • kernel-64k-debug-core as a component of Red Hat Enterprise Linux 10
  • kernel-64k-debug-devel as a component of Red Hat Enterprise Linux 10
  • kernel-64k-debug-devel-matched as a component of Red Hat Enterprise Linux 10
  • kernel-64k-debug-modules as a component of Red Hat Enterprise Linux 10
  • kernel-64k-debug-modules-core as a component of Red Hat Enterprise Linux 10
  • kernel-64k-debug-modules-extra as a component of Red Hat Enterprise Linux 10
  • kernel-64k-devel as a component of Red Hat Enterprise Linux 10
  • kernel-64k-devel-matched as a component of Red Hat Enterprise Linux 10
Summary
A flaw was found in ksmbd, a Linux kernel module that provides an in-kernel Server Message Block (SMB) server. When processing an SMB1 negotiate request as an SMB2 server operation, a slab-out-of-bounds memory error occurs in the `init_smb2_rsp_hdr` function. This vulnerability could allow a remote attacker to disclose sensitive information or cause a denial of service.
Remediation
No remediation text is recorded.
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2023-60438

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Fix not verified
01

What, why and how

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix slab-out-of-bounds in init_smb2_rsp_hdr When smb1 mount fails, KASAN detect slab-out-of-bounds in init_smb2_rsp_hdr like the following one. For smb1 negotiate(56bytes) , init_smb2_rsp_hdr() for smb2 is called. The issue occurs while handling smb1 negotiate as smb2 server operations. Add smb server operations for smb1 (get_cmd_val, init_rsp_hdr, allocate_rsp_buf, check_user_session) to handle smb1 negotiate so that smb2 server operation does not handle it. [ 411.400423] CIFS: VFS: Use of the less secure dialect vers=1.0 is not recommended unless required for access to very old servers [ 411.400452] CIFS: Attempting to mount \\192.168.45.139\homes [ 411.479312] ksmbd: init_smb2_rsp_hdr : 492 [ 411.479323] ================================================================== [ 411.479327] BUG: KASAN: slab-out-of-bounds in init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479369] Read of size 16 at addr ffff888488ed0734 by task kworker/14:1/199 [ 411.479379] CPU: 14 PID: 199 Comm: kworker/14:1 Tainted: G OE 6.1.21 #3 [ 411.479386] Hardware name: ASUSTeK COMPUTER INC. Z10PA-D8 Series/Z10PA-D8 Series, BIOS 3801 08/23/2019 [ 411.479390] Workqueue: ksmbd-io handle_ksmbd_work [ksmbd] [ 411.479425] Call Trace: [ 411.479428] <TASK> [ 411.479432] dump_stack_lvl+0x49/0x63 [ 411.479444] print_report+0x171/0x4a8 [ 411.479452] ? kasan_complete_mode_report_info+0x3c/0x200 [ 411.479463] ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479497] kasan_report+0xb4/0x130 [ 411.479503] ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479537] kasan_check_range+0x149/0x1e0 [ 411.479543] memcpy+0x24/0x70 [ 411.479550] init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479585] handle_ksmbd_work+0x109/0x760 [ksmbd] [ 411.479616] ? _raw_spin_unlock_irqrestore+0x50/0x50 [ 411.479624] ? smb3_encrypt_resp+0x340/0x340 [ksmbd] [ 411.479656] process_one_work+0x49c/0x790 [ 411.479667] worker_thread+0x2b1/0x6e0 [ 411.479674] ? process_one_work+0x790/0x790 [ 411.479680] kthread+0x177/0x1b0 [ 411.479686] ? kthread_complete_and_exit+0x30/0x30 [ 411.479692] ret_from_fork+0x22/0x30 [ 411.479702] </TASK>

What

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix slab-out-of-bounds in init_smb2_rsp_hdr When smb1 mount fails, KASAN detect slab-out-of-bounds in init_smb2_rsp_hdr like the following one. For smb1 negotiate(56bytes) , init_smb2_rsp_hdr() for smb2 is called. The issue occurs while handling smb1 negotiate as smb2 server operations. Add smb server operations for smb1 (get_cmd_val, init_rsp_hdr, allocate_rsp_buf, check_user_session) to handle smb1 negotiate so that smb2 server operation does not handle it. [ 411.400423] CIFS: VFS: Use of the less secure dialect vers=1.0 is not recommended unless required for access to very old servers [ 411.400452] CIFS: Attempting to mount \\192.168.45.139\homes [ 411.479312] ksmbd: init_smb2_rsp_hdr : 492 [ 411.479323] ================================================================== [ 411.479327] BUG: KASAN: slab-out-of-bounds in init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479369] Read of size 16 at addr ffff888488ed0734 by task kworker/14:1/199 [ 411.479379] CPU: 14 PID: 199 Comm: kworker/14:1 Tainted: G OE 6.1.21 #3 [ 411.479386] Hardware name: ASUSTeK COMPUTER INC. Z10PA-D8 Series/Z10PA-D8 Series, BIOS 3801 08/23/2019 [ 411.479390] Workqueue: ksmbd-io handle_ksmbd_work [ksmbd] [ 411.479425] Call Trace: [ 411.479428] <TASK> [ 411.479432] dump_stack_lvl+0x49/0x63 [ 411.479444] print_report+0x171/0x4a8 [ 411.479452] ? kasan_complete_mode_report_info+0x3c/0x200 [ 411.479463] ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479497] kasan_report+0xb4/0x130 [ 411.479503] ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479537] kasan_check_range+0x149/0x1e0 [ 411.479543] memcpy+0x24/0x70 [ 411.479550] init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479585] handle_ksmbd_work+0x109/0x760 [ksmbd] [ 411.479616] ? _raw_spin_unlock_irqrestore+0x50/0x50 [ 411.479624] ? smb3_encrypt_resp+0x340/0x340 [ksmbd] [ 411.479656] process_one_work+0x49c/0x790 [ 411.479667] worker_thread+0x2b1/0x6e0 [ 411.479674] ? process_one_work+0x790/0x790 [ 411.479680] kthread+0x177/0x1b0 [ 411.479686] ? kthread_complete_and_exit+0x30/0x30 [ 411.479692] ret_from_fork+0x22/0x30 [ 411.479702] </TASK>

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix slab-out-of-bounds in init_smb2_rsp_hdr When smb1 mount fails, KASAN detect slab-out-of-bounds in init_smb2_rsp_hdr like the following one. For smb1 negotiate(56bytes) , init_smb2_rsp_hdr() for smb2 is called. The issue occurs while handling smb1 negotiate as smb2 server operations. Add smb server operations for smb1 (get_cmd_val, init_rsp_hdr, allocate_rsp_buf, check_user_session) to handle smb1 negotiate so that smb2 server operation does not handle it. [ 411.400423] CIFS: VFS: Use of the less secure dialect vers=1.0 is not recommended unless required for access to very old servers [ 411.400452] CIFS: Attempting to mount \\192.168.45.139\homes [ 411.479312] ksmbd: init_smb2_rsp_hdr : 492 [ 411.479323] ================================================================== [ 411.479327] BUG: KASAN: slab-out-of-bounds in init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479369] Read of size 16 at addr ffff888488ed0734 by task kworker/14:1/199 [ 411.479379] CPU: 14 PID: 199 Comm: kworker/14:1 Tainted: G OE 6.1.21 #3 [ 411.479386] Hardware name: ASUSTeK COMPUTER INC. Z10PA-D8 Series/Z10PA-D8 Series, BIOS 3801 08/23/2019 [ 411.479390] Workqueue: ksmbd-io handle_ksmbd_work [ksmbd] [ 411.479425] Call Trace: [ 411.479428] <TASK> [ 411.479432] dump_stack_lvl+0x49/0x63 [ 411.479444] print_report+0x171/0x4a8 [ 411.479452] ? kasan_complete_mode_report_info+0x3c/0x200 [ 411.479463] ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479497] kasan_report+0xb4/0x130 [ 411.479503] ? init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479537] kasan_check_range+0x149/0x1e0 [ 411.479543] memcpy+0x24/0x70 [ 411.479550] init_smb2_rsp_hdr+0x1e2/0x1f4 [ksmbd] [ 411.479585] handle_ksmbd_work+0x109/0x760 [ksmbd] [ 411.479616] ? _raw_spin_unlock_irqrestore+0x50/0x50 [ 411.479624] ? smb3_encrypt_resp+0x340/0x340 [ksmbd] [ 411.479656] process_one_work+0x49c/0x790 [ 411.479667] worker_thread+0x2b1/0x6e0 [ 411.479674] ? process_one_work+0x790/0x790 [ 411.479680] kthread+0x177/0x1b0 [ 411.479686] ? kthread_complete_and_exit+0x30/0x30 [ 411.479692] ret_from_fork+0x22/0x30 [ 411.479702] </TASK>

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → vulnerable operation → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration.
CWE not yet assigned
CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticated
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2025-2941Linux Kernel: Mehrere Schwachstellen ermöglichen Denial of Service

Ein Angreifer kann diese Schwachstellen ausnutzen, um nicht näher spezifizierte Angriffe durchzuführen, die möglicherweise zu Denial‑of‑Service, Speicherbeschädigung oder weiteren nicht definierten Auswirkungen führen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20251231Security Bulletin 31 Dec 2025

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 31 Dec 2025, published on 31 December 2025. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix not verified
Affected
Linux: 51a8534c0f35c0401e45f1055f914729cad98bf9 < 921536046bd165efeb07beef5630aff35cd6a489, 0b3ec5671ac06829ccebdaeec05acedfec327f42 < a8334a0c535d0f0b4d64926c8fe0922ed98f7d43, cc32cd98a0aee4cc3eb611cbce11795b1aaa738a < 99a51c673b1d2d0b5a972353401b77612d9cc713, 39b291b86b5988bf8753c3874d5c773399d09b96 < dc8289f912387c3bcfbc5d2db29c8947fa207c11, 5.15.105 < 5.15.145, 6.1.22 < 6.1.24, 6.2.9 < 6.2.11
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 30 Dec 2025 · Last source change 5 Aug 2026, 09:18 UTC · CWE not yet assigned

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2023-60438
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceUnavailable
NVD statusNVD not scheduled

Missing structured fields: CWE classification. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2023-60438↗Vendor CSAF · Red Hat Product Security↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2023-54203 · cve.blacktree.nl