CVE-2026-31444 (GCVE-0-2026-31444)
Vulnerability from cvelistv5 – Published: 2026-04-22 13:53 – Updated: 2026-08-05 12:22
VLAI
EPSS
VEX
Title
ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()
Summary
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()
smb_grant_oplock() has two issues in the oplock publication sequence:
1) opinfo is linked into ci->m_op_list (via opinfo_add) before
add_lease_global_list() is called. If add_lease_global_list()
fails (kmalloc returns NULL), the error path frees the opinfo
via __free_opinfo() while it is still linked in ci->m_op_list.
Concurrent m_op_list readers (opinfo_get_list, or direct iteration
in smb_break_all_levII_oplock) dereference the freed node.
2) opinfo->o_fp is assigned after add_lease_global_list() publishes
the opinfo on the global lease list. A concurrent
find_same_lease_key() can walk the lease list and dereference
opinfo->o_fp->f_ci while o_fp is still NULL.
Fix by restructuring the publication sequence to eliminate post-publish
failure:
- Set opinfo->o_fp before any list publication (fixes NULL deref).
- Preallocate lease_table via alloc_lease_table() before opinfo_add()
so add_lease_global_list() becomes infallible after publication.
- Keep the original m_op_list publication order (opinfo_add before
lease list) so concurrent opens via same_client_has_lease() and
opinfo_get_list() still see the in-flight grant.
- Use opinfo_put() instead of __free_opinfo() on err_out so that
the RCU-deferred free path is used.
This also requires splitting add_lease_global_list() to take a
preallocated lease_table and changing its return type from int to void,
since it can no longer fail.
Severity
9.8 (Critical)
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
302fef75512b2c8329a3f5efab1ae7ba2562387a , < 9e785f004cbc56390479b77375726ea9b0d1a8a6
(git)
Affected: 08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c , < 7de55bba69cbf0f9280daaea385daf08bc076121 (git) Affected: 1d6abf145615dbfe267ce3b0a271f95e3780e18e , < a5c6f6d6ceefed2d5210ee420fb75f8362461f46 (git) Affected: ce8507ee82c888126d8e7565e27c016308d24cde , < 6d7e5a918c1d0aad06db0e17677b66fc9a471021 (git) Affected: 1dfd062caa165ec9d7ee0823087930f3ab8a6294 , < 48623ec358c1c600fa1e38368746f933e0f1a617 (git) |
guessed | |
| Linux | Linux |
Affected:
6.6.130 , < 6.6.131
(semver)
Affected: 6.12.78 , < 6.12.80 (semver) Affected: 6.18.19 , < 6.18.21 (semver) Affected: 6.19.9 , < 6.19.11 (semver) |
guessed |
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}
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}
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free and NULL deref in smb_grant_oplock()\n\nsmb_grant_oplock() has two issues in the oplock publication sequence:\n\n1) opinfo is linked into ci-\u003em_op_list (via opinfo_add) before\n add_lease_global_list() is called. If add_lease_global_list()\n fails (kmalloc returns NULL), the error path frees the opinfo\n via __free_opinfo() while it is still linked in ci-\u003em_op_list.\n Concurrent m_op_list readers (opinfo_get_list, or direct iteration\n in smb_break_all_levII_oplock) dereference the freed node.\n\n2) opinfo-\u003eo_fp is assigned after add_lease_global_list() publishes\n the opinfo on the global lease list. A concurrent\n find_same_lease_key() can walk the lease list and dereference\n opinfo-\u003eo_fp-\u003ef_ci while o_fp is still NULL.\n\nFix by restructuring the publication sequence to eliminate post-publish\nfailure:\n\n- Set opinfo-\u003eo_fp before any list publication (fixes NULL deref).\n- Preallocate lease_table via alloc_lease_table() before opinfo_add()\n so add_lease_global_list() becomes infallible after publication.\n- Keep the original m_op_list publication order (opinfo_add before\n lease list) so concurrent opens via same_client_has_lease() and\n opinfo_get_list() still see the in-flight grant.\n- Use opinfo_put() instead of __free_opinfo() on err_out so that\n the RCU-deferred free path is used.\n\nThis also requires splitting add_lease_global_list() to take a\npreallocated lease_table and changing its return type from int to void,\nsince it can no longer fail."
}
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"id": "CVE-2026-31444",
"lastModified": "2026-06-17T10:33:43.960",
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"id": "CVE-2026-31444",
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"title": "kernel: ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()",
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"version": "3"
},
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"aggregate_severity": "moderate",
"current_release_date": "2026-09-11T01:32:04Z",
"cve": "CVE-2026-31444",
"id": "CVE-2026-31444",
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"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-31444",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-31444.json",
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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