{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99110","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-25T10:25:14.392Z","datePublished":"2026-10-28T10:34:28.239Z","dateUpdated":"2026-10-31T12:43:03.377Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-10-31T12:43:03.377Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix heap overflow in cifs_do_set_acl()\n\ncifs_set_acl() validates ACL size using posix_acl_xattr_size():\n\n        4 + (count * 8)  // 4-byte header + 8 bytes per ACE\n\ncifs_do_set_acl() then calls posix_acl_to_cifs() to write the CIFS\nwire format into the same buffer:\n\n        6 + (count * 10)  // 6-byte header + 10 bytes per ACE\n\nAn ACL that passes the xattr-based check in cifs_set_acl() can\noverflow the heap when posix_acl_to_cifs() writes the larger CIFS\nformat.\n\nValidate the CIFS format size against the remaining buffer space and\nUSHRT_MAX before converting--data_count is __u16, so sizes above\nUSHRT_MAX truncate the on-wire packet length, causing the server to\napply a partial ACL.  Replace MaxDataCount = 1000 with\nmin(CIFSMaxBufSize, USHRT_MAX)."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - setxattr(2) on system.posix_acl_access/default flows through do_set_acl() → set_posix_acl() → cifs_set_acl() → patched cifs_do_set_acl(); the oversized ACL originates in the local xattr, while SMB_COM_TRANSACTION2 is only an outbound request.\nAC:H - The copy is deterministic once reached, but it requires default-off CONFIG_CIFS_POSIX, an SMB1 mount, and server negotiation of CIFS_UNIX_POSIX_ACL_CAP to set SB_POSIXACL. An unprivileged local attacker cannot create that mount or capability state.\nPR:L - set_posix_acl() gates the path with inode_owner_or_capable(), so an ordinary user who owns a file on the mounted share can submit the ACL without capabilities; on a non-multiuser mount cifs_sb_tlink() simply reuses the master tcon.\nUI:N - The attacker directly invokes setxattr() or fsetxattr() on their CIFS inode, causing cifs_set_acl() to run without any separate victim action after the qualifying mount exists.\nS:U - posix_acl_to_cifs() overwrites the client kernel's cifs_request slab, and any resulting kernel compromise remains within the same host security authority rather than crossing a VM, IOMMU, or sandbox boundary.\nC:H - cifs_init_ace() emits attacker-shaped 10-byte tag, permission, and uid/gid records past the cifs_request object; with the supported 8KiB CIFSMaxBufSize, the overflow reaches neighboring request objects. This controllable slab corruption can be groomed into reuse or overlap and kernel-memory disclosure.\nI:H - posix_acl_to_cifs() writes a multi-kilobyte out-of-bounds stream whose ACE tags, permissions, and 32-bit uid/gid values are caller-selected; corrupting adjacent request or allocator state provides heap-write and control-flow-hijack potential.\nA:H - With default CIFSMaxBufSize=16384, 2047 valid entries pass cifs_set_acl()'s 16380-byte check but make posix_acl_to_cifs() write 20476 bytes, nearly 4KiB beyond the 16588-byte allocation before SendReceive() rejects the frame. Repeated calls can oops or panic the kernel."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifssmb.c"],"versions":[{"version":"dc1af4c4b4721abfa07b351063825acc7e69cc66","lessThan":"68652afb9b9adf70125971abee9b95341e042249","status":"affected","versionType":"git"},{"version":"dc1af4c4b4721abfa07b351063825acc7e69cc66","lessThan":"9312a00215602ba028495ef3fa00fb84af0478e0","status":"affected","versionType":"git"},{"version":"dc1af4c4b4721abfa07b351063825acc7e69cc66","lessThan":"d96f3365ce61c5f39602955af43c8174548dee98","status":"affected","versionType":"git"},{"version":"dc1af4c4b4721abfa07b351063825acc7e69cc66","lessThan":"596b4062e6c75bdd85a7f2b7f2087a872dc420ac","status":"affected","versionType":"git"},{"version":"dc1af4c4b4721abfa07b351063825acc7e69cc66","lessThan":"1dac61e2c29d1a71784604b48cf3b1234a65ec29","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/client/cifssmb.c"],"versions":[{"version":"6.2","status":"affected"},{"version":"0","lessThan":"6.2","status":"unaffected","versionType":"semver"},{"version":"6.6.161","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.115","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.59","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.13","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.6.161"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.12.115"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"6.18.59"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"7.2.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.2","versionEndExcluding":"7.3"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/68652afb9b9adf70125971abee9b95341e042249"},{"url":"https://git.kernel.org/stable/c/9312a00215602ba028495ef3fa00fb84af0478e0"},{"url":"https://git.kernel.org/stable/c/d96f3365ce61c5f39602955af43c8174548dee98"},{"url":"https://git.kernel.org/stable/c/596b4062e6c75bdd85a7f2b7f2087a872dc420ac"},{"url":"https://git.kernel.org/stable/c/1dac61e2c29d1a71784604b48cf3b1234a65ec29"}],"title":"smb: client: fix heap overflow in cifs_do_set_acl()","x_generator":{"engine":"bippy-1.2.0"}}}}