{"id":"CVE-2026-74631","state":"PUBLISHED","title":"net: smc: fix splice entry lifetime imbalance in smc_rx_splice","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: smc: fix splice entry lifetime imbalance in smc_rx_splice\n\nsmc_rx_splice() passes pages to splice_to_pipe() before taking the\nreferences that cover the lifetime of each splice entry. In the\nVM-backed RMB path, splice_to_pipe() may drop unqueued entries through\nsmc_rx_spd_release(), while queued entries are released later via the\npipe buffer callback.\n\nThe old post-splice accounting also derives the number of queued VM pages\nfrom an offset mutated while building the descriptor, and a multi-page\nsplice pairs one sock_hold() with multiple sock_put() calls.\n\nTake the page and socket references for every candidate entry before\nsplice_to_pipe(), and drop the matching private state, page reference,\nand socket reference from smc_rx_spd_release() for entries that never\nget queued. This fixes a refcount imbalance that can underflow page\nrefcounts and trigger a use-after-free.","publishedAt":"2026-08-22T15:32:12.334Z","updatedAt":"2026-10-16T19:06:03.774Z","severity":{"score":8.4,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/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":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"7ddc7af2ae7fc5a0c0635b245c0824c8b76de5cb","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"07ad246529d136d5ef441d5ab4c305d132ff3090","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"c841789e456ec6751342fa800639ce8e82ff0e6b","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"af02c67ce654356c58db20a0bb2db33ace3b07a8","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"ca8342b5fc24c249fdb998468f6a168b457c67e5","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"0b7d54cedea5cb158e21925ae0c6c2f5c87ed2a0","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"4515c78f4d9fd577270f012efeb062ea58b3682d","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"5d9686af2976741bbd79b150d1c9e60b81e7f12e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_rx.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.18","versionType":"semver"},{"version":"5.10.266","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.217","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.152","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_rx.c"]}],"references":["https://git.kernel.org/stable/c/7ddc7af2ae7fc5a0c0635b245c0824c8b76de5cb","https://git.kernel.org/stable/c/07ad246529d136d5ef441d5ab4c305d132ff3090","https://git.kernel.org/stable/c/c841789e456ec6751342fa800639ce8e82ff0e6b","https://git.kernel.org/stable/c/af02c67ce654356c58db20a0bb2db33ace3b07a8","https://git.kernel.org/stable/c/ca8342b5fc24c249fdb998468f6a168b457c67e5","https://git.kernel.org/stable/c/0b7d54cedea5cb158e21925ae0c6c2f5c87ed2a0","https://git.kernel.org/stable/c/4515c78f4d9fd577270f012efeb062ea58b3682d","https://git.kernel.org/stable/c/5d9686af2976741bbd79b150d1c9e60b81e7f12e"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74631.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74631","state":"PUBLISHED","datePublished":"2026-08-22T15:32:12.334Z","dateUpdated":"2026-10-16T19:06:03.774Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.922Z"},"containers":{"cna":{"title":"net: smc: fix splice entry lifetime imbalance in smc_rx_splice","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: smc: fix splice entry lifetime imbalance in smc_rx_splice\n\nsmc_rx_splice() passes pages to splice_to_pipe() before taking the\nreferences that cover the lifetime of each splice entry. In the\nVM-backed RMB path, splice_to_pipe() may drop unqueued entries through\nsmc_rx_spd_release(), while queued entries are released later via the\npipe buffer callback.\n\nThe old post-splice accounting also derives the number of queued VM pages\nfrom an offset mutated while building the descriptor, and a multi-page\nsplice pairs one sock_hold() with multiple sock_put() calls.\n\nTake the page and socket references for every candidate entry before\nsplice_to_pipe(), and drop the matching private state, page reference,\nand socket reference from smc_rx_spd_release() for entries that never\nget queued. This fixes a refcount imbalance that can underflow page\nrefcounts and trigger a use-after-free."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"7ddc7af2ae7fc5a0c0635b245c0824c8b76de5cb","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"07ad246529d136d5ef441d5ab4c305d132ff3090","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"c841789e456ec6751342fa800639ce8e82ff0e6b","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"af02c67ce654356c58db20a0bb2db33ace3b07a8","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"ca8342b5fc24c249fdb998468f6a168b457c67e5","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"0b7d54cedea5cb158e21925ae0c6c2f5c87ed2a0","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"4515c78f4d9fd577270f012efeb062ea58b3682d","versionType":"git"},{"version":"9014db202cb764b8e14c53e7bacc81f9a1a2ba7f","status":"affected","lessThan":"5d9686af2976741bbd79b150d1c9e60b81e7f12e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_rx.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.18","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.18","versionType":"semver"},{"version":"5.10.266","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.217","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.152","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/smc/smc_rx.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/7ddc7af2ae7fc5a0c0635b245c0824c8b76de5cb"},{"url":"https://git.kernel.org/stable/c/07ad246529d136d5ef441d5ab4c305d132ff3090"},{"url":"https://git.kernel.org/stable/c/c841789e456ec6751342fa800639ce8e82ff0e6b"},{"url":"https://git.kernel.org/stable/c/af02c67ce654356c58db20a0bb2db33ace3b07a8"},{"url":"https://git.kernel.org/stable/c/ca8342b5fc24c249fdb998468f6a168b457c67e5"},{"url":"https://git.kernel.org/stable/c/0b7d54cedea5cb158e21925ae0c6c2f5c87ed2a0"},{"url":"https://git.kernel.org/stable/c/4515c78f4d9fd577270f012efeb062ea58b3682d"},{"url":"https://git.kernel.org/stable/c/5d9686af2976741bbd79b150d1c9e60b81e7f12e"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":8.4,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - smc_rx_splice is only reached via splice()/tee() on an SMC socket FD (syscall -> smc_splice_read -> smc_rx_recvmsg with pipe set); remote SMC peers can supply receive-buffer data but cannot execute the vulnerable splice path without a local process invoking splice on that socket.\nAC:L - The attacker controls splice length, can nearly fill the destination pipe to force splice_to_pipe to drop unqueued entries via smc_rx_spd_release, and can hit the multi-page VM-backed RMB path (smcr_buf_type or mixed-buffer vmalloc fallback); no timing race or external victim state is required.\nPR:N - Exploitation requires only completing an SMC session as a network peer to a victim that reads with splice (common zero-copy SMC pattern); no local account, capabilities, or namespace-admin rights on the victim host are needed beyond normal remote connectivity to the SMC service.\nUI:N - No per-exploit victim action is needed beyond an application already using splice on SMC receive; a malicious peer can deliver the receive data while the victim's normal automated splice path triggers the refcount imbalance without prompts or manual steps.\nS:U - Impact is kernel page refcount underflow and use-after-free within the same kernel security boundary, enabling privilege escalation or crash on the host; it does not cross VM, IOMMU, or sandbox authority boundaries.\nC:H - Refcount imbalance lets smc_rx_spd_release and pipe-buffer teardown free pages while still referenced, creating a UAF on RMB pages that can be turned into arbitrary kernel memory disclosure via heap reuse and spraying.\nI:H - Corrupted page lifetime and dangling pipe_buffer state enable heap metadata corruption and arbitrary kernel writes from the UAF primitive, supporting control-flow hijacking and local privilege escalation.\nA:H - Page refcount underflow and UAF during splice teardown can cause immediate kernel oops/panic; repeated splice from an SMC peer reliably triggers denial-of-service even when full exploitation is not attempted."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-25T05:40:55.722Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"5.10.266"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"5.15.217"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"6.6.152"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"6.12.104"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"6.18.45"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"7.1.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.18","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74631","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T19:03:01.320271Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:06:03.774Z"}}]}}}