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Linux Distros Unpatched Vulnerability : CVE-2026-89648
medium Nessus Plugin ID 345266
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Synopsis
The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.Description
The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.- ceph: cap delegated inode count in ceph_parse_deleg_inos() ceph_parse_deleg_inos() decodes interval sets of delegated inode numbers from an MDS create-with-delegation reply. For each set it reads a 64-bit start and a 64-bit len with ceph_decode_64_safe(), which only validates that the eight bytes are present in the message, not the value, and then loops over len while inserting entries into s_delegated_inos. len is fully attacker controlled. A malicious or compromised MDS can send one huge interval, many intervals in one reply, duplicate intervals, or repeated replies that accumulate delegated inodes on the same session.
The original code bounded none of these and could spin the insert loop or grow the xarray without limit.
Bound both dimensions with a single enforcement point. Track the number of delegated inodes held by each MDS session in an atomic counter and grow it only in ceph_insert_deleg_ino(), which uses atomic_add_unless() to refuse to push the count past CEPH_MAX_DELEG_INOS. Because that helper is the only place the counter grows, the per-session population can never exceed the cap, so no separate per-session pre-check is needed. The counter is decremented when async create consumes a delegated inode or when an insert fails, incremented when a delegated inode is restored, initialized with the session xarray, and reset when reconnect destroys the xarray. A per-session cap alone still lets one reply spin the insert loop on duplicate ranges without growing the counter, so also cap the aggregate interval length accepted from a single reply. Together these bound both the loop trip count per reply and the xarray population across replies. The cap is a fixed, client-chosen constant rather than a value derived from the MDS.
mds_client_prealloc_inos is a userspace MDS configuration option; it is never sent to the kernel client on the wire, and a server-supplied bound could not be trusted for a defensive limit in any case. The constant is set well above that option's documented default of 1000 (a generous multiple), so legitimate refill behavior is unaffected while the CPU and xarray memory a malformed delegation stream can consume stays bounded. Impact: a malicious or compromised Ceph MDS can no longer make a client spin through an unbounded delegated-inode interval or grow one session's delegated-inode xarray without limit. (CVE-2026-89648)
Note that Nessus relies on the presence of the package as reported by the vendor.
Solution
There is no known solution at this time.See Also
Plugin Details
Severity: Medium
ID: 345266
File Name: unpatched_CVE_2026_89648.nasl
Version: 1.1
Type: Local
Agent: unix
Family: Misc.
Published: 9/12/2026
Updated: 9/12/2026
Supported Sensors: Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 6.2
Percentile: 96.39
CVSS v2
Risk Factor: Medium
Base Score: 5.4
Temporal Score: 4.6
Vector: CVSS2#AV:L/AC:M/Au:N/C:N/I:P/A:C
CVSS Score Source: CVE-2026-89648
CVSS v3
Risk Factor: Medium
Base Score: 6.1
Temporal Score: 5.6
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
Temporal Vector: CVSS:3.0/E:U/RL:U/RC:C
Vulnerability Information
CPE: cpe:/o:debian:debian_linux:12.0, cpe:/o:debian:debian_linux:13.0, cpe:/o:debian:debian_linux:14.0, p-cpe:/a:debian:debian_linux:linux
Required KB Items: Host/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched, Host/OS/identifier
Exploit Ease: No known exploits are available
Vulnerability Publication Date: 9/11/2026
Reference Information
CVE: CVE-2026-89648