{"id":"CVE-2026-31539","state":"PUBLISHED","title":"smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: smbdirect: introduce smbdirect_socket.recv_io.credits.available\n\nThe logic off managing recv credits by counting posted recv_io and\ngranted credits is racy.\n\nThat's because the peer might already consumed a credit,\nbut between receiving the incoming recv at the hardware\nand processing the completion in the 'recv_done' functions\nwe likely have a window where we grant credits, which\ndon't really exist.\n\nSo we better have a decicated counter for the\navailable credits, which will be incremented\nwhen we posted new recv buffers and drained when\nwe grant the credits to the peer.","publishedAt":"2026-04-24T14:30:26.326Z","updatedAt":"2026-10-19T18:55:58.491Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5fb9b459b3686e366640edd4e62805ef7b4de927","status":"affected","lessThan":"e811e60e1cc79923c4388146eb1fa26a7482731e","versionType":"git"},{"version":"5fb9b459b3686e366640edd4e62805ef7b4de927","status":"affected","lessThan":"f99996870222b598914a1f49d7375dc23752c237","versionType":"git"},{"version":"5fb9b459b3686e366640edd4e62805ef7b4de927","status":"affected","lessThan":"6e3c5052f9686192e178806e017b7377155f4bab","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/common/smbdirect/smbdirect_socket.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.18","versionType":"semver"},{"version":"6.18.11","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.1","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/common/smbdirect/smbdirect_socket.h"]}],"references":["https://git.kernel.org/stable/c/e811e60e1cc79923c4388146eb1fa26a7482731e","https://git.kernel.org/stable/c/f99996870222b598914a1f49d7375dc23752c237","https://git.kernel.org/stable/c/6e3c5052f9686192e178806e017b7377155f4bab"],"weaknesses":["CWE-362"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31539.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31539","state":"PUBLISHED","datePublished":"2026-04-24T14:30:26.326Z","dateUpdated":"2026-10-19T18:55:58.491Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.114Z"},"containers":{"cna":{"title":"smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: smbdirect: introduce smbdirect_socket.recv_io.credits.available\n\nThe logic off managing recv credits by counting posted recv_io and\ngranted credits is racy.\n\nThat's because the peer might already consumed a credit,\nbut between receiving the incoming recv at the hardware\nand processing the completion in the 'recv_done' functions\nwe likely have a window where we grant credits, which\ndon't really exist.\n\nSo we better have a decicated counter for the\navailable credits, which will be incremented\nwhen we posted new recv buffers and drained when\nwe grant the credits to the peer."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5fb9b459b3686e366640edd4e62805ef7b4de927","status":"affected","lessThan":"e811e60e1cc79923c4388146eb1fa26a7482731e","versionType":"git"},{"version":"5fb9b459b3686e366640edd4e62805ef7b4de927","status":"affected","lessThan":"f99996870222b598914a1f49d7375dc23752c237","versionType":"git"},{"version":"5fb9b459b3686e366640edd4e62805ef7b4de927","status":"affected","lessThan":"6e3c5052f9686192e178806e017b7377155f4bab","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/common/smbdirect/smbdirect_socket.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.18","versionType":"semver"},{"version":"6.18.11","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.1","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/common/smbdirect/smbdirect_socket.h"]}],"references":[{"url":"https://git.kernel.org/stable/c/e811e60e1cc79923c4388146eb1fa26a7482731e"},{"url":"https://git.kernel.org/stable/c/f99996870222b598914a1f49d7375dc23752c237"},{"url":"https://git.kernel.org/stable/c/6e3c5052f9686192e178806e017b7377155f4bab"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - SMBDirect is reached by a remote RDMA peer through RDMA CM listeners on SMBDirect/SMB ports such as 5445 and 445. The ksmbd server path processes the affected negotiation and data-transfer credit handling from network-originated RDMA messages.\nAC:L - The issue is a receive-credit accounting race, but the remote peer can repeatedly drive both message arrival and credit-request/response behavior with crafted SMBDirect traffic. No unusual victim state or uncontrollable condition is required beyond an enabled SMBDirect RDMA deployment.\nPR:N - The server-side path accepts the RDMA connection and performs SMBDirect negotiation and data-transfer credit handling before SMB session authentication. A remote peer does not need SMB credentials to reach the vulnerable credit logic.\nUI:N - Exploitation against the server path requires only network/RDMA traffic from the attacker. No local user or administrator action is needed after the service is exposed.\nS:U - The impact remains within the kernel SMBDirect/SMB service security authority. There is no VM escape, IOMMU bypass, or cross-authority boundary crossing.\nC:N - The bug overgrants receive credits but does not expose a kernel read primitive; incoming payload bounds are checked before reassembly. An RDMA send without a posted receive should produce transport/RNR failure rather than disclose memory.\nI:N - The investigation did not identify an arbitrary write or memory-corruption primitive. The false credit causes receive-queue/transport state inconsistency, not attacker-controlled modification of kernel data.\nA:H - False credits can allow the peer to send when no real receive buffer is posted, causing RDMA QP/transport errors and SMBDirect disconnects with RNR retries disabled. Because this is remotely and unauthenticatedly repeatable against the exposed SMBDirect service, availability impact is high."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:23:24.146Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"6.18.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"6.19.1"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-31539","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:10:46.426998Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-362","lang":"en","type":"CWE","description":"CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:55:58.491Z"}}]}}}