{"id":"CVE-2026-74270","state":"PUBLISHED","title":"handshake: Require admin permission for DONE command","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nhandshake: Require admin permission for DONE command\n\nACCEPT and DONE are the two downcalls of the handshake genl\nfamily, both intended for use by the trusted handshake agent\n(tlshd). ACCEPT already requires GENL_ADMIN_PERM; DONE has\nno privilege check at all.\n\nThe fd-lookup in handshake_nl_done_doit() only confirms that\nsome pending handshake request exists for the supplied sockfd;\nit does not authenticate the sender. An unprivileged process\nthat guesses or observes a valid sockfd can therefore submit\na DONE with HANDSHAKE_A_DONE_STATUS == 0, leaving the kernel\nconsumer to proceed as if the handshake succeeded. A non-zero\nstatus on a forged DONE tears down a legitimate in-flight\nhandshake before tlshd can report its real result.","publishedAt":"2026-08-15T05:57:44.195Z","updatedAt":"2026-10-16T18:55:29.298Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/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":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"25fb53e43ec006ac69b9e825a7e8a11d63a6083e","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"b6557f912509abe8e70223373dd7a44d1d4a0d6c","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"67cec2f1eb9e58719d622e92e2278ceda72dbd85","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"4dafc411948469277b276724c3b2b4408c02c04c","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"81246a65303d9635266b1334490142caaf86a11f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["Documentation/netlink/specs/handshake.yaml","net/handshake/genl.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","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":["Documentation/netlink/specs/handshake.yaml","net/handshake/genl.c"]}],"references":["https://git.kernel.org/stable/c/25fb53e43ec006ac69b9e825a7e8a11d63a6083e","https://git.kernel.org/stable/c/b6557f912509abe8e70223373dd7a44d1d4a0d6c","https://git.kernel.org/stable/c/67cec2f1eb9e58719d622e92e2278ceda72dbd85","https://git.kernel.org/stable/c/4dafc411948469277b276724c3b2b4408c02c04c","https://git.kernel.org/stable/c/81246a65303d9635266b1334490142caaf86a11f"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74270.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74270","state":"PUBLISHED","datePublished":"2026-08-15T05:57:44.195Z","dateUpdated":"2026-10-16T18:55:29.298Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.879Z"},"containers":{"cna":{"title":"handshake: Require admin permission for DONE command","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nhandshake: Require admin permission for DONE command\n\nACCEPT and DONE are the two downcalls of the handshake genl\nfamily, both intended for use by the trusted handshake agent\n(tlshd). ACCEPT already requires GENL_ADMIN_PERM; DONE has\nno privilege check at all.\n\nThe fd-lookup in handshake_nl_done_doit() only confirms that\nsome pending handshake request exists for the supplied sockfd;\nit does not authenticate the sender. An unprivileged process\nthat guesses or observes a valid sockfd can therefore submit\na DONE with HANDSHAKE_A_DONE_STATUS == 0, leaving the kernel\nconsumer to proceed as if the handshake succeeded. A non-zero\nstatus on a forged DONE tears down a legitimate in-flight\nhandshake before tlshd can report its real result."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"25fb53e43ec006ac69b9e825a7e8a11d63a6083e","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"b6557f912509abe8e70223373dd7a44d1d4a0d6c","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"67cec2f1eb9e58719d622e92e2278ceda72dbd85","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"4dafc411948469277b276724c3b2b4408c02c04c","versionType":"git"},{"version":"3b3009ea8abb713b022d94fba95ec270cf6e7eae","status":"affected","lessThan":"81246a65303d9635266b1334490142caaf86a11f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["Documentation/netlink/specs/handshake.yaml","net/handshake/genl.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.4","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","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":["Documentation/netlink/specs/handshake.yaml","net/handshake/genl.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/25fb53e43ec006ac69b9e825a7e8a11d63a6083e"},{"url":"https://git.kernel.org/stable/c/b6557f912509abe8e70223373dd7a44d1d4a0d6c"},{"url":"https://git.kernel.org/stable/c/67cec2f1eb9e58719d622e92e2278ceda72dbd85"},{"url":"https://git.kernel.org/stable/c/4dafc411948469277b276724c3b2b4408c02c04c"},{"url":"https://git.kernel.org/stable/c/81246a65303d9635266b1334490142caaf86a11f"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - Exploitation requires sending a HANDSHAKE_CMD_DONE generic-netlink message via a local netlink socket to handshake_nl_done_doit(); although nfsd and nvmet-tcp are network-facing, the vulnerable control-plane downcall is not reachable from remote packets.\nAC:L - Once a process holds a sockfd for a socket with a pending handshake request, forging DONE with status 0 or a failure status is a single deterministic netlink operation; the commit describes sockfd guessing/observation as sufficient and no special timing beyond normal concurrency is required.\nPR:L - Before the fix, HANDSHAKE_CMD_DONE lacked GENL_ADMIN_PERM while ACCEPT required it, so any unprivileged local user with netlink access could invoke the handler without CAP_NET_ADMIN in the initial user namespace or any other elevated capability.\nUI:N - Exploitation does not require victim interaction such as opening files or mounting filesystems; the attacker sends a forged DONE netlink message directly to complete or abort an in-flight kernel handshake.\nS:U - Impact is confined to kernel TLS handshake state for local socket consumers (NFS RPC-over-TLS, NVMe-oF TCP TLS); it does not cross a VM, container, or IOMMU security boundary into a different authority.\nC:H - A forged DONE with HANDSHAKE_A_DONE_STATUS==0 makes kernel consumers proceed as if tlshd completed TLS successfully, bypassing X.509/PSK peer verification on NFS and NVMe-oF TCP sessions and undermining confidentiality of protected network storage traffic.\nI:H - The attacker can supply arbitrary HANDSHAKE_A_DONE_REMOTE_AUTH peer-identity values with a forged success, causing nfsd/nvmet to mark connections as TLS-authenticated and continue I/O under false security assumptions, corrupting integrity of access-control decisions.\nA:H - A forged DONE with non-zero status calls handshake_complete() with an error, tearing down legitimate in-flight handshakes before tlshd reports the real result and denying or disrupting TLS session establishment on NFS/NVMe-oF TCP services."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T05:45:16.772Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-74270","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T18:51:52.912027Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T18:55:29.298Z"}}]}}}