{"id":"CVE-2026-89650","state":"PUBLISHED","title":"ceph: bound num_export_targets array for mds info v2/v3","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: bound num_export_targets array for mds info v2/v3\n\nceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from\neach per-mds info record and advances the decode cursor by\nnum_export_targets * sizeof(u32) without first checking that many bytes\nremain. The only upper-bound check that catches a runaway cursor\n(*p > info_end) is gated on info_v >= 4, because info_end is left NULL\nfor info_v 2 and 3. When the monitor sends an MDS map whose per-mds\ninfo version is 2 or 3 with an oversized num_export_targets, the cursor\nmoves past the message front buffer and the later export-targets loop\ncalls the unchecked ceph_decode_32() on out-of-bounds memory.\n\nA kernel client processes CEPH_MSG_MDS_MAP from its monitor session\n(net/ceph/mon_client.c dispatches it; fs/ceph/super.c routes it to\nceph_mdsc_handle_mdsmap(), which sets end to the front buffer bound and\ncalls ceph_mdsmap_decode()). A malicious or compromised monitor, or an\non-path attacker on an unsigned/unencrypted messenger session, can\ntherefore drive an out-of-bounds read in the client kernel; on x86_64\nwith KASAN it is reported as a slab-out-of-bounds read in\nceph_mdsmap_decode(). The decoded values land in the internal\ninfo->export_targets[] array, so the consequence is a kernel\nout-of-bounds read, not an information leak to the attacker.\n\nImpact: a malicious or compromised Ceph monitor sending an MDS map with\na per-mds info version of 2 or 3 and an oversized num_export_targets\nfield triggers an out-of-bounds read in the CephFS client kernel.\n\nAdd a ceph_decode_need() for the export-targets array before advancing\nthe cursor, so the bound is enforced for every info_v >= 2, not only\ninfo_v >= 4. This mirrors the count-then-need idiom already used for\nm_data_pg_pools later in the same function.\n\nCompute the export-targets byte count with size_mul() and reuse that\nchecked length when advancing the cursor, so the attacker-controlled\nnum_export_targets multiplication fails closed on overflow rather than\nrelying on the later kcalloc() guard.","publishedAt":"2026-09-11T19:45:40.867Z","updatedAt":"2026-10-30T12:32:31.274Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"a6eaf7bd229d0940ba8f126c684a663a680abef1","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"0c4bcc3ba7291d383b82ce1c2fe324f69a42da2d","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"55a06b32438c222765138727d0a8164b103e8f0d","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"3bf7dba8dba9a05774b846affec61a3624ddba38","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"58c2d3e954c13694ef6e820a5e9456461bb9e7df","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"332c444f4dc6fa1e8b8637c9e82d29e97f768656","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"a3eb169ee297aa99670ba927c659990bd1e453f3","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ceph/mdsmap.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.7","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ceph/mdsmap.c"]}],"references":["https://git.kernel.org/stable/c/a6eaf7bd229d0940ba8f126c684a663a680abef1","https://git.kernel.org/stable/c/0c4bcc3ba7291d383b82ce1c2fe324f69a42da2d","https://git.kernel.org/stable/c/55a06b32438c222765138727d0a8164b103e8f0d","https://git.kernel.org/stable/c/eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911","https://git.kernel.org/stable/c/3bf7dba8dba9a05774b846affec61a3624ddba38","https://git.kernel.org/stable/c/58c2d3e954c13694ef6e820a5e9456461bb9e7df","https://git.kernel.org/stable/c/332c444f4dc6fa1e8b8637c9e82d29e97f768656","https://git.kernel.org/stable/c/a3eb169ee297aa99670ba927c659990bd1e453f3"],"weaknesses":[],"ingestedAt":"2026-10-30T12:50:04.827Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/89xxx/CVE-2026-89650.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89650","state":"PUBLISHED","datePublished":"2026-09-11T19:45:40.867Z","dateUpdated":"2026-10-30T12:32:31.274Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-11T19:38:34.742Z"},"containers":{"cna":{"title":"ceph: bound num_export_targets array for mds info v2/v3","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: bound num_export_targets array for mds info v2/v3\n\nceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from\neach per-mds info record and advances the decode cursor by\nnum_export_targets * sizeof(u32) without first checking that many bytes\nremain. The only upper-bound check that catches a runaway cursor\n(*p > info_end) is gated on info_v >= 4, because info_end is left NULL\nfor info_v 2 and 3. When the monitor sends an MDS map whose per-mds\ninfo version is 2 or 3 with an oversized num_export_targets, the cursor\nmoves past the message front buffer and the later export-targets loop\ncalls the unchecked ceph_decode_32() on out-of-bounds memory.\n\nA kernel client processes CEPH_MSG_MDS_MAP from its monitor session\n(net/ceph/mon_client.c dispatches it; fs/ceph/super.c routes it to\nceph_mdsc_handle_mdsmap(), which sets end to the front buffer bound and\ncalls ceph_mdsmap_decode()). A malicious or compromised monitor, or an\non-path attacker on an unsigned/unencrypted messenger session, can\ntherefore drive an out-of-bounds read in the client kernel; on x86_64\nwith KASAN it is reported as a slab-out-of-bounds read in\nceph_mdsmap_decode(). The decoded values land in the internal\ninfo->export_targets[] array, so the consequence is a kernel\nout-of-bounds read, not an information leak to the attacker.\n\nImpact: a malicious or compromised Ceph monitor sending an MDS map with\na per-mds info version of 2 or 3 and an oversized num_export_targets\nfield triggers an out-of-bounds read in the CephFS client kernel.\n\nAdd a ceph_decode_need() for the export-targets array before advancing\nthe cursor, so the bound is enforced for every info_v >= 2, not only\ninfo_v >= 4. This mirrors the count-then-need idiom already used for\nm_data_pg_pools later in the same function.\n\nCompute the export-targets byte count with size_mul() and reuse that\nchecked length when advancing the cursor, so the attacker-controlled\nnum_export_targets multiplication fails closed on overflow rather than\nrelying on the later kcalloc() guard."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"a6eaf7bd229d0940ba8f126c684a663a680abef1","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"0c4bcc3ba7291d383b82ce1c2fe324f69a42da2d","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"55a06b32438c222765138727d0a8164b103e8f0d","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"3bf7dba8dba9a05774b846affec61a3624ddba38","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"58c2d3e954c13694ef6e820a5e9456461bb9e7df","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"332c444f4dc6fa1e8b8637c9e82d29e97f768656","versionType":"git"},{"version":"d463a43d69f4af85887671d76182437775fd1631","status":"affected","lessThan":"a3eb169ee297aa99670ba927c659990bd1e453f3","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ceph/mdsmap.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.7","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.221","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.188","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.157","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.109","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.50","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.4","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/ceph/mdsmap.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a6eaf7bd229d0940ba8f126c684a663a680abef1"},{"url":"https://git.kernel.org/stable/c/0c4bcc3ba7291d383b82ce1c2fe324f69a42da2d"},{"url":"https://git.kernel.org/stable/c/55a06b32438c222765138727d0a8164b103e8f0d"},{"url":"https://git.kernel.org/stable/c/eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911"},{"url":"https://git.kernel.org/stable/c/3bf7dba8dba9a05774b846affec61a3624ddba38"},{"url":"https://git.kernel.org/stable/c/58c2d3e954c13694ef6e820a5e9456461bb9e7df"},{"url":"https://git.kernel.org/stable/c/332c444f4dc6fa1e8b8637c9e82d29e97f768656"},{"url":"https://git.kernel.org/stable/c/a3eb169ee297aa99670ba927c659990bd1e453f3"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H","baseScore":9.1,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - CEPH_MSG_MDS_MAP arrives over the kernel Ceph messenger TCP session from a monitor (mon_dispatch/extra_mon_dispatch) or MDS (mds_dispatch) and is decoded in ceph_mdsmap_decode(); a malicious cluster peer or on-path attacker on an unsigned msgr session reaches the bug with network data alone.\nAC:L - The attacker fully controls per-mds info_v and num_export_targets; setting info_v to 2 or 3 (so info_end stays NULL) and an oversized count deterministically advances the cursor past msg->front and hits unchecked ceph_decode_32(), with no race or victim memory layout required.\nPR:N - The attacker acts as the remote Ceph monitor or MDS peer (or MITM on msgr1/crc or auth_none); no local account, capability, or privilege on the victim CephFS client host is required.\nUI:N - Once CephFS is mounted, the kernel client subscribes to MDS maps and ceph_mdsc_handle_mdsmap() runs automatically on each update; no further mount, open, or interactive victim action is required at exploit time.\nS:U - The out-of-bounds read, any leaked heap bytes, and a possible oops stay inside the victim host kernel CephFS client and do not cross a VM, container, IOMMU, or other security authority.\nC:H - An attacker-chosen num_export_targets drives an unbounded loop of unchecked ceph_decode_32() reads past the message front slab into adjacent kernel heap (KASAN slab-out-of-bounds); per kernel guidance an unbounded out-of-bounds read is Confidentiality High.\nI:N - OOB words are copied only into a correctly sized kcalloc'd export_targets array; overshooting the front buffer then fails later ceph_decode_32_safe() so the map is destroyed and never installed, giving no out-of-bounds write or control-flow primitive.\nA:H - Walking an attacker-chosen number of u32s past the kmalloc'd msg->front object into unmapped or guarded pages oopses the ceph-msgr worker, and a failed decode also shuts down the mount via ceph_umount_begin(); both are repeatable on each crafted map."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:32:31.274Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"5.15.221"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.1.188"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.12.109"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.7","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-89650","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T19:25:14.842752Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T19:26:46.677Z"}}]}}}