{"id":"CVE-2026-43376","state":"PUBLISHED","title":"ksmbd: fix use-after-free by using call_rcu() for oplock_info","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free by using call_rcu() for oplock_info\n\nksmbd currently frees oplock_info immediately using kfree(), even\nthough it is accessed under RCU read-side critical sections in places\nlike opinfo_get() and proc_show_files().\n\nSince there is no RCU grace period delay between nullifying the pointer\nand freeing the memory, a reader can still access oplock_info\nstructure after it has been freed. This can leads to a use-after-free\nespecially in opinfo_get() where atomic_inc_not_zero() is called on\nalready freed memory.\n\nFix this by switching to deferred freeing using call_rcu().","publishedAt":"2026-05-08T14:21:25.854Z","updatedAt":"2026-08-05T12:27:35.730Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"296cb5457cc6f4a754c4ae29855f8a253d52bcc6","status":"affected","lessThan":"302fef75512b2c8329a3f5efab1ae7ba2562387a","versionType":"git"},{"version":"d54ab1520d43e95f9b2e22d7a05fc9614192e5a5","status":"affected","lessThan":"08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c","versionType":"git"},{"version":"18b4fac5ef17f77fed9417d22210ceafd6525fc7","status":"affected","lessThan":"1d6abf145615dbfe267ce3b0a271f95e3780e18e","versionType":"git"},{"version":"18b4fac5ef17f77fed9417d22210ceafd6525fc7","status":"affected","lessThan":"ce8507ee82c888126d8e7565e27c016308d24cde","versionType":"git"},{"version":"18b4fac5ef17f77fed9417d22210ceafd6525fc7","status":"affected","lessThan":"1dfd062caa165ec9d7ee0823087930f3ab8a6294","versionType":"git"},{"version":"d73686367ad68534257cd88a36ca3c52cb8b81d8","status":"affected","versionType":"git"},{"version":"6.6.88","status":"affected","lessThan":"6.6.130","versionType":"semver"},{"version":"6.12.25","status":"affected","lessThan":"6.12.78","versionType":"semver"},{"version":"6.14.4","status":"affected","lessThan":"6.15","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/oplock.c","fs/smb/server/oplock.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/oplock.c","fs/smb/server/oplock.h"]}],"references":["https://git.kernel.org/stable/c/302fef75512b2c8329a3f5efab1ae7ba2562387a","https://git.kernel.org/stable/c/08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c","https://git.kernel.org/stable/c/1d6abf145615dbfe267ce3b0a271f95e3780e18e","https://git.kernel.org/stable/c/ce8507ee82c888126d8e7565e27c016308d24cde","https://git.kernel.org/stable/c/1dfd062caa165ec9d7ee0823087930f3ab8a6294"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43376.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43376","state":"PUBLISHED","datePublished":"2026-05-08T14:21:25.854Z","dateUpdated":"2026-08-05T12:27:35.730Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:56.006Z"},"containers":{"cna":{"title":"ksmbd: fix use-after-free by using call_rcu() for oplock_info","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free by using call_rcu() for oplock_info\n\nksmbd currently frees oplock_info immediately using kfree(), even\nthough it is accessed under RCU read-side critical sections in places\nlike opinfo_get() and proc_show_files().\n\nSince there is no RCU grace period delay between nullifying the pointer\nand freeing the memory, a reader can still access oplock_info\nstructure after it has been freed. This can leads to a use-after-free\nespecially in opinfo_get() where atomic_inc_not_zero() is called on\nalready freed memory.\n\nFix this by switching to deferred freeing using call_rcu()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"296cb5457cc6f4a754c4ae29855f8a253d52bcc6","status":"affected","lessThan":"302fef75512b2c8329a3f5efab1ae7ba2562387a","versionType":"git"},{"version":"d54ab1520d43e95f9b2e22d7a05fc9614192e5a5","status":"affected","lessThan":"08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c","versionType":"git"},{"version":"18b4fac5ef17f77fed9417d22210ceafd6525fc7","status":"affected","lessThan":"1d6abf145615dbfe267ce3b0a271f95e3780e18e","versionType":"git"},{"version":"18b4fac5ef17f77fed9417d22210ceafd6525fc7","status":"affected","lessThan":"ce8507ee82c888126d8e7565e27c016308d24cde","versionType":"git"},{"version":"18b4fac5ef17f77fed9417d22210ceafd6525fc7","status":"affected","lessThan":"1dfd062caa165ec9d7ee0823087930f3ab8a6294","versionType":"git"},{"version":"d73686367ad68534257cd88a36ca3c52cb8b81d8","status":"affected","versionType":"git"},{"version":"6.6.88","status":"affected","lessThan":"6.6.130","versionType":"semver"},{"version":"6.12.25","status":"affected","lessThan":"6.12.78","versionType":"semver"},{"version":"6.14.4","status":"affected","lessThan":"6.15","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/oplock.c","fs/smb/server/oplock.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/oplock.c","fs/smb/server/oplock.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/302fef75512b2c8329a3f5efab1ae7ba2562387a"},{"url":"https://git.kernel.org/stable/c/08aa9f3c8cf4d0bee44df540dfe34e8d64069f2c"},{"url":"https://git.kernel.org/stable/c/1d6abf145615dbfe267ce3b0a271f95e3780e18e"},{"url":"https://git.kernel.org/stable/c/ce8507ee82c888126d8e7565e27c016308d24cde"},{"url":"https://git.kernel.org/stable/c/1dfd062caa165ec9d7ee0823087930f3ab8a6294"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - ksmbd is the in-kernel SMB server reachable over TCP/445, and the vulnerable oplock_info lifetime is exercised by remote SMB2 create/close/oplock and lease operations.\nAC:L - The attacker can create oplocks/leases and drive concurrent requests over SMB connections, so the race is attacker-controlled rather than dependent on an external victim condition.\nPR:N - The path is post-session/tree-connect, but ksmbd supports guest/public shares; in the highest reasonable oplocks-enabled guest-share deployment, no prior credentials are needed.\nUI:N - No victim user action is required once the SMB service and share are available; the attacker sends network protocol requests directly.\nS:U - The vulnerable component and impacted resources are the same kernel/host security authority, with no VM, hypervisor, or other scope boundary crossing.\nC:H - This is a kernel heap use-after-free on oplock_info, including stale pointer dereferences after freed memory can be reallocated, which can reasonably enable high-impact kernel information disclosure.\nI:H - The stale atomic_inc_not_zero and later field accesses can corrupt a reallocated kernel object, making arbitrary kernel memory modification or code execution defensible.\nA:H - The UAF can directly trigger kernel memory corruption, oops, panic, or hang, causing high availability impact."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:27:35.730Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.88","versionEndExcluding":"6.6.130"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.25","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.18.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.19.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.0"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14.4"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}