CVE-2026-99083 (GCVE-0-2026-99083)
Vulnerability from cvelistv5
Published
2026-10-23 12:45
Modified
2026-10-30 12:41
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 676392184785ace61e939831e7ca44a03d438c3b Version: ef572ffa8eb44111eed2925fbb2adca78bdcbf61 Version: 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 Version: 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 Version: 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 Version: 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 Version: 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 Version: 2ba03cecb12ac7ac9e0170e251543c56832d9959 Version: 5.15.145 ≤ Version: 6.1.40 ≤ Version: 6.4.5 ≤ |
||
{
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{
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}
],
"cpeApplicability": [
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix heap out-of-bounds write in krb5_authenticate()\n\nIn krb5_authenticate(), out_len is calculated to determine available\nheadroom in response_buf for the incoming Kerberos AP-REP token. However,\nwhen SMB2_SESSION_SETUP is processed as a non-first element of a compounded\nSMB2 request, the calculation omits work-\u003enext_smb2_rsp_hdr_off.\n\nThis causes out_len to overstate remaining buffer headroom by\nthe cumulative size of prior responses in the compound chain. Consequently,\nthe length check in ksmbd_krb5_authenticate()\n(*out_len \u003c= resp-\u003espnego_blob_len) passes erroneously, allowing memcpy()\nto write the AP-REP blob past the end of response_buf into adjacent kernel\nheap memory.\n\nFix this by subtracting work-\u003enext_smb2_rsp_hdr_off when computing out_len,\nensuring it accurately reflects physical remaining buffer space."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - ksmbd_conn_handler_loop() receives the compound request over TCP/445, and __process_request() dispatches its non-first SMB2 SESSION_SETUP to smb2_sess_setup() and krb5_authenticate(). The SESSION_SETUP SecurityBuffer carries the Kerberos AP-REQ that produces the AP-REP copied by the patched path.\nAC:L - The same authenticated peer can create directory entries, request a sized QUERY_DIRECTORY response, and place SESSION_SETUP later in the compound, controlling next_smb2_rsp_hdr_off before supplying its valid AP-REQ; no race or external actor is required.\nPR:L - ksmbd_krb5_authenticate() checks KSMBD_USER_FLAG_OK before its length check and memcpy; ksmbd.mountd sets it only after krb5_rd_req() accepts the AP-REQ and usm_handle_login_request() recognizes the account. An ordinary valid Kerberos account suffices, but an unauthenticated peer cannot reach the write.\nUI:N - The peer opens the session, prepares the prior compound response, and sends the Kerberos SESSION_SETUP itself; no victim user must open, mount, or approve anything.\nS:U - ksmbd_krb5_authenticate() corrupts memory adjacent to the host kernel\u0027s response_buf allocation; this remains within the same kernel security authority and crosses no VM, IOMMU, or sandbox boundary.\nC:H - The AP-REP memcpy in ksmbd_krb5_authenticate() can overrun response_buf and corrupt adjacent heap objects; exploitable kernel heap corruption can be converted into a memory-read primitive exposing arbitrary kernel data.\nI:H - The memcpy writes resp-\u003espnego_blob_len AP-REP bytes beyond response_buf into adjacent kernel heap memory, enabling corruption of object metadata or control data and potential kernel code execution.\nA:H - Writing the AP-REP beyond response_buf can corrupt adjacent allocations or allocator metadata and trigger KASAN, an oops, or a kernel panic; the authenticated SMB peer can repeat the compound request."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-30T12:41:38.581Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/a07dfb33112a42437f9d2d0bfd35c68575257381"
},
{
"url": "https://git.kernel.org/stable/c/1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ff"
},
{
"url": "https://git.kernel.org/stable/c/59c6dcc5dd9dafe764ca0d40525933b2be69b059"
},
{
"url": "https://git.kernel.org/stable/c/80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a"
},
{
"url": "https://git.kernel.org/stable/c/517404e157395d0f8da125ca956c566895dfcd06"
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{
"url": "https://git.kernel.org/stable/c/4722d06b2907585074252061b1024a696c1cfc23"
},
{
"url": "https://git.kernel.org/stable/c/23a0be6a84a38ac169eeab49017934e8e27c65f0"
}
],
"title": "ksmbd: fix heap out-of-bounds write in krb5_authenticate()",
"x_generator": {
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}
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"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-99083",
"datePublished": "2026-10-23T12:45:01.735Z",
"dateReserved": "2026-09-25T10:25:14.390Z",
"dateUpdated": "2026-10-30T12:41:38.581Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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