{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-80527", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-26T14:34:25.764Z", "datePublished": "2026-08-26T14:37:06.178Z", "dateUpdated": "2026-10-16T19:26:24.678Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-27T05:01:22.018Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix hanging __ceph_get_caps() with stale mds_wanted\n\nA reader can hang forever in __ceph_get_caps() when the client no\nlonger holds `FILE_RD`, but local cap state still says that the\ncapability is already wanted (via `mds_wanted`).\n\nOne way to trigger this is through MDS cap revocation. If another\nclient performs a conflicting operation, the MDS can revoke `FILE_RD`\nfrom the reader; the next read then has to reacquire `FILE_RD`. If\nthe cap update that should request `FILE_RD` never reaches the MDS\nafter `cap->mds_wanted` was raised, the reader is left holding only\nnon-file caps while local `mds_wanted` still includes the file read\ncaps.\n\nIn that state, try_get_cap_refs() sees `need <= mds_wanted` and\nreturns 0, so __ceph_get_caps() just waits on `i_cap_wq`. If the cap\nupdate that was supposed to request `FILE_RD never reaches the MDS\nafter `cap->mds_wanted was` raised, no further request is sent and the\nwaiter can sleep indefinitely until unrelated cap traffic happens to\nwake it up.\n\nThe ordering issue is that `cap->mds_wanted` is updated in\n__prep_cap() before the `CEPH_MSG_CLIENT_CAPS message` is actually\nqueued for send. That makes one field serve two different meanings at\nonce: what this client wants, and what the client believes the MDS\nalready knows it wants.\n\nA proper fix would be to split those states and track whether a cap\nupdate is actually in flight or has been observed by the MDS.\nHowever, simply moving the `cap->mds_wanted assignment` later would\nnot be sufficient: queueing the message in the messenger does not\nguarantee that the MDS processed that specific wanted set, and\nreconnect or message loss can still invalidate that assumption.\nFixing that properly would require a larger rework of the cap state\nmachine.\n\nTo allow simpler backports to stable kernels, this patch implements a\nsimpler workaround:\n\n- stop waiting forever in __ceph_get_caps(); after a bounded wait,\n fall back to the renew path\n\n- make ceph_renew_caps() issue a synchronous `OPEN` request whenever\n the inode still does not actually hold the wanted caps, instead of\n only calling ceph_check_caps()\n\nThe extra issued-vs-wanted check in ceph_renew_caps() is necessary\nbecause the previous test only checked whether the inode still had any\nreal caps at all. That is not enough after revocation: the client can\nstill hold something like `pLs` and yet be missing `FILE_RD`\ncompletely. In that case, falling back to ceph_check_caps() is not\nsufficient, because it still trusts `cap->mds_wanted` and may resend\nnothing. By requiring `(issued & wanted) == wanted` before taking the\nasynchronous path, the code only uses ceph_check_caps() when the\n`wanted caps` are already actually issued. Otherwise, it sends the\nsynchronous `OPEN` renew.\n\nThis preserves the existing asynchronous fast path when the wanted\ncaps are already issued, avoids changing cap-state semantics, and\nfixes the hang by guaranteeing that a stalled waiter eventually\nretries through a path that does not rely on the stale `mds_wanted`\nstate.\n\n[ idryomov: move CEPH_GET_CAPS_WAIT_TIMEOUT from libceph.h to\n mds_client.h, formatting ]" } ], "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 - On nodes with cephfs mounted (common in Ceph/Rook/Kubernetes), a remote Ceph client can perform conflicting writes so the MDS revokes FILE_RD via CEPH_MSG_CLIENT_CAPS over the network; the victim kernel then hits the stale mds_wanted hang on the next VFS read/mmap/ioctl path into __ceph_get_caps().\nAC:L - The fix commit documents MDS cap revocation from another client as a reliable trigger; an attacker controls both sides by holding a second Ceph client session and driving conflicting I/O and reconnect/message-loss timing, without depending on uncontrollable victim heap layout or rare kernel configs.\nPR:N - Exploitation requires no Linux account, capability, or init-namespace root on the victim host; any remote (or co-tenant) Ceph client with write access to the shared file can induce revocation and the hang while victims only perform normal reads on an already-mounted cephfs export.\nUI:N - No interactive victim action is needed beyond routine automated reads on cephfs-backed workloads; the attacker does not require the victim to mount media, click a link, or perform a one-off administrative step at exploitation time.\nS:U - Impact is confined to threads blocked in __ceph_get_caps() on the same host kernel security domain; it does not cross VM, container, or IOMMU boundaries or grant elevated privileges beyond availability loss on the affected client.\nC:N - This is a capability wait-loop logic error with no out-of-bounds access, use-after-free, or information disclosure; stale mds_wanted only prevents cap reacquisition and does not read or leak kernel or file data to an attacker.\nI:N - The bug does not modify inode data, kernel memory, or capabilities; it causes indefinite sleeping in cap acquisition with no path to arbitrary write, metadata corruption, or code execution.\nA:H - Before the fix, __ceph_get_caps() could wait forever on i_cap_wq when mds_wanted falsely indicated FILE_RD was already requested but not issued, hanging the reader thread (read/write/mmap/getattr) until unrelated cap traffic; repeated exploitation can deny service to cephfs-backed applications." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ceph/caps.c", "fs/ceph/file.c", "fs/ceph/mds_client.h" ], "versions": [ { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "b5661524c5a45085a866864ca9b8ae2513dfd67a", "status": "affected", "versionType": "git" }, { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "5e84bc6f67e19fdd192d8b215de728acbfc12572", "status": "affected", "versionType": "git" }, { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "5fedf279a1ea369d39c8b06dd4547cdc576065d0", "status": "affected", "versionType": "git" }, { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "e05c315b4da0c16ea800ee4b2cb6c617f586d1b5", "status": "affected", "versionType": "git" }, { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "fcce1b3be6d286aa80831e730289f4c062053ae6", "status": "affected", "versionType": "git" }, { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "a3bc6b3e9ef3f5f5cb85a902a30a090c7931127c", "status": "affected", "versionType": "git" }, { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "9e55fe24c548ad3163903eb58bb002d28d32a630", "status": "affected", "versionType": "git" }, { "version": "0a454bdd501ad1aa30bb72e9581efa338ad6ce5c", "lessThan": "50958bb928bad3bdba9e5d1b7ff4bbadcf6951e6", "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/ceph/caps.c", "fs/ceph/file.c", "fs/ceph/mds_client.h" ], "versions": [ { "version": "5.8", "status": "affected" }, { "version": "0", "lessThan": "5.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.266", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.217", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.184", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.153", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.105", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.46", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.10", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "5.8", "versionEndExcluding": "5.10.266" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "5.15.217" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "6.1.184" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "6.6.153" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "6.12.105" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "6.18.46" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "7.1.10" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.8", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/b5661524c5a45085a866864ca9b8ae2513dfd67a" }, { "url": "https://git.kernel.org/stable/c/5e84bc6f67e19fdd192d8b215de728acbfc12572" }, { "url": "https://git.kernel.org/stable/c/5fedf279a1ea369d39c8b06dd4547cdc576065d0" }, { "url": "https://git.kernel.org/stable/c/e05c315b4da0c16ea800ee4b2cb6c617f586d1b5" }, { "url": "https://git.kernel.org/stable/c/fcce1b3be6d286aa80831e730289f4c062053ae6" }, { "url": "https://git.kernel.org/stable/c/a3bc6b3e9ef3f5f5cb85a902a30a090c7931127c" }, { "url": "https://git.kernel.org/stable/c/9e55fe24c548ad3163903eb58bb002d28d32a630" }, { "url": "https://git.kernel.org/stable/c/50958bb928bad3bdba9e5d1b7ff4bbadcf6951e6" } ], "title": "ceph: fix hanging __ceph_get_caps() with stale mds_wanted", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-80527", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:16:34.310764Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:24.678Z" } } ] } }