{"id":"CVE-2026-23364","state":"PUBLISHED","title":"ksmbd: Compare MACs in constant time","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: Compare MACs in constant time\n\nTo prevent timing attacks, MAC comparisons need to be constant-time.\nReplace the memcmp() with the correct function, crypto_memneq().","publishedAt":"2026-03-25T10:27:46.960Z","updatedAt":"2026-10-15T01:14:22.928Z","severity":{"score":7.4,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","source":"Linux"},"assigner":"Linux","products":["Linux 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- ksmbd is the in-kernel SMB server listening on TCP port 445, directly reachable by any network attacker.\nAC:H - This is a timing side-channel attack requiring many network requests to statistically distinguish memcmp() early-return timing differences; network jitter is beyond the attacker's control and adds noise that significantly increases exploitation difficulty.\nPR:N - The most critical vulnerable comparison (NTLMv2 MAC in ksmbd_auth_ntlmv2) is reached during the SMB session setup authentication handshake, before any credentials are verified — no prior privileges are needed.\nUI:N - The attacker directly sends SMB authentication requests to the ksmbd server; no victim user action is required.\nS:U - The vulnerability and its impact remain within the ksmbd/kernel security authority; no security boundary is crossed.\nC:H - Successful timing attack on the NTLMv2 MAC comparison enables authentication bypass, granting the attacker full read access to all SMB-shared files and data.\nI:H - Authentication bypass via forged NTLMv2 response grants write access to SMB shares, allowing arbitrary modification of shared data.\nA:N - The timing side-channel itself causes no crashes, hangs, or denial of service; it only leaks timing information about MAC 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