--- id: CVE-2026-89650 title: 'ceph: bound num_export_targets array for mds info v2/v3' summary: |- In the Linux kernel, the following vulnerability has been resolved: ceph: bound num_export_targets array for mds info v2/v3 ceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from each per-mds info record and advances th… severity: critical cvss: 9.1 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H' cvssSource: cna cwe: - CWE-125 vendor: Linux product: Linux affected: - >- Linux >= d463a43d69f4af85887671d76182437775fd1631 < 0c4bcc3ba7291d383b82ce1c2fe324f69a42da2d - >- Linux >= d463a43d69f4af85887671d76182437775fd1631 < 55a06b32438c222765138727d0a8164b103e8f0d - >- Linux >= d463a43d69f4af85887671d76182437775fd1631 < eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911 - >- Linux >= d463a43d69f4af85887671d76182437775fd1631 < 3bf7dba8dba9a05774b846affec61a3624ddba38 - >- Linux >= d463a43d69f4af85887671d76182437775fd1631 < 58c2d3e954c13694ef6e820a5e9456461bb9e7df - >- Linux >= d463a43d69f4af85887671d76182437775fd1631 < 332c444f4dc6fa1e8b8637c9e82d29e97f768656 - >- Linux >= d463a43d69f4af85887671d76182437775fd1631 < a3eb169ee297aa99670ba927c659990bd1e453f3 - Linux 4.7 ssvc: exploitation: none automatable: 'yes' technicalImpact: partial timestamp: '2026-10-16T19:25:14.842752Z' published: '2026-09-11' updated: '2026-10-19' sourceUpdated: '2026-10-19T08:50:21.912Z' source: CVEORG sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89650' references: - 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' - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89650.json - url: 'https://access.redhat.com/security/cve/CVE-2026-89650' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532105' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89650' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89650' - url: >- https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89650.mbox tags: - cve.org - csaf - vex - red-hat - score-dispute epss: 0.00502 epssPercentile: 0.42785 scores: cna: 9.1 vendor: 7 ingestedAt: '2026-09-14T15:23:07.450Z' --- ## Overview In the Linux kernel, the following vulnerability has been resolved: ceph: bound num_export_targets array for mds info v2/v3 ceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from each per-mds info record and advances the decode cursor by num_export_targets * sizeof(u32) without first checking that many bytes remain. The only upper-bound check that catches a runaway cursor (*p > info_end) is gated on info_v >= 4, because info_end is left NULL for info_v 2 and 3. When the monitor sends an MDS map whose per-mds info version is 2 or 3 with an oversized num_export_targets, the cursor moves past the message front buffer and the later export-targets loop calls the unchecked ceph_decode_32() on out-of-bounds memory. A kernel client processes CEPH_MSG_MDS_MAP from its monitor session (net/ceph/mon_client.c dispatches it; fs/ceph/super.c routes it to ceph_mdsc_handle_mdsmap(), which sets end to the front buffer bound and calls ceph_mdsmap_decode()). A malicious or compromised monitor, or an on-path attacker on an unsigned/unencrypted messenger session, can therefore drive an out-of-bounds read in the client kernel; on x86_64 with KASAN it is reported as a slab-out-of-bounds read in ceph_mdsmap_decode(). The decoded values land in the internal info->export_targets[] array, so the consequence is a kernel out-of-bounds read, not an information leak to the attacker. Impact: a malicious or compromised Ceph monitor sending an MDS map with a per-mds info version of 2 or 3 and an oversized num_export_targets field triggers an out-of-bounds read in the CephFS client kernel. Add a ceph_decode_need() for the export-targets array before advancing the cursor, so the bound is enforced for every info_v >= 2, not only info_v >= 4. This mirrors the count-then-need idiom already used for m_data_pg_pools later in the same function. Compute the export-targets byte count with size_mul() and reuse that checked length when advancing the cursor, so the attacker-controlled num_export_targets multiplication fails closed on overflow rather than relying on the later kcalloc() guard. ## Affected - `Linux >= d463a43d69f4af85887671d76182437775fd1631 < 0c4bcc3ba7291d383b82ce1c2fe324f69a42da2d` - `Linux >= d463a43d69f4af85887671d76182437775fd1631 < 55a06b32438c222765138727d0a8164b103e8f0d` - `Linux >= d463a43d69f4af85887671d76182437775fd1631 < eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911` - `Linux >= d463a43d69f4af85887671d76182437775fd1631 < 3bf7dba8dba9a05774b846affec61a3624ddba38` - `Linux >= d463a43d69f4af85887671d76182437775fd1631 < 58c2d3e954c13694ef6e820a5e9456461bb9e7df` - `Linux >= d463a43d69f4af85887671d76182437775fd1631 < 332c444f4dc6fa1e8b8637c9e82d29e97f768656` - `Linux >= d463a43d69f4af85887671d76182437775fd1631 < a3eb169ee297aa99670ba927c659990bd1e453f3` - `Linux 4.7` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89650.json)