VulnerabilityPublished 11 Sep 2026Updated 30 Oct 2026

CVE-2026-89650: Linux kernel · ceph: bound num_export_targets array for mds info v2/v3

Affects Linux kernelSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical · fixed in eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911 : patch Linux kernel as a priority.

Data as of 30 Oct 2026, 13:04 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (Linux)	CVSS 3.1	9.1

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-10-16.

Patch

Available – fixed in eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911, a6eaf7bd229d0940ba8f126c684a663a680abef1, a3eb169ee297aa99670ba927c659990bd1e453f3 +5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ d463a43d69f4af85887671d76182437775fd1631, < eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911	Fixed in eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911
LinuxLinux	Affected ≥ d463a43d69f4af85887671d76182437775fd1631, < a6eaf7bd229d0940ba8f126c684a663a680abef1	Fixed in a6eaf7bd229d0940ba8f126c684a663a680abef1
LinuxLinux	Affected ≥ d463a43d69f4af85887671d76182437775fd1631, < a3eb169ee297aa99670ba927c659990bd1e453f3	Fixed in a3eb169ee297aa99670ba927c659990bd1e453f3
LinuxLinux	Affected ≥ d463a43d69f4af85887671d76182437775fd1631, < 332c444f4dc6fa1e8b8637c9e82d29e97f768656	Fixed in 332c444f4dc6fa1e8b8637c9e82d29e97f768656
LinuxLinux	Affected ≥ d463a43d69f4af85887671d76182437775fd1631, < 58c2d3e954c13694ef6e820a5e9456461bb9e7df	Fixed in 58c2d3e954c13694ef6e820a5e9456461bb9e7df
LinuxLinux	Affected ≥ d463a43d69f4af85887671d76182437775fd1631, < 55a06b32438c222765138727d0a8164b103e8f0d	Fixed in 55a06b32438c222765138727d0a8164b103e8f0d

AI-suggested

A fix is available and has been applied in multiple Linux kernel commits. Users should update their Linux kernel to a version including the fixes identified by the commits (e.g., eb3e1a1cb1634c76d59c5a9cb1a026fc69d40911 and others). No additional mitigation is required if the kernel is updated. There is no indication that the vulnerability is exploitable in the wild currently.

Description

CVE-2026-89650 is a critical vulnerability in the Linux kernel's Ceph filesystem client. It involves an out-of-bounds read triggered by a malicious or compromised Ceph monitor sending a specially crafted MDS map with an oversized num_export_targets field in per-mds info version 2 or 3. This flaw allows the kernel client to read beyond the intended buffer boundaries, potentially causing a denial of service. The vulnerability has been fixed by adding proper bounds checking for all relevant info versions and safely handling the export-targets array length calculation.

Impact

A malicious or compromised Ceph monitor can send a crafted MDS map that triggers an out-of-bounds read in the CephFS client kernel, potentially causing a denial of service or kernel instability. The vulnerability does not result in information disclosure but can impact kernel integrity and availability. The CVSS v3.1 score is 9.1 (critical) due to network attack vector, no privileges required, no user interaction, and high impact on confidentiality and availability.

Summary

The vulnerability exists in the ceph_mdsmap_decode() function in the Linux kernel, where num_export_targets is read from each per-mds info record and used to advance a decode cursor without sufficient bounds checking for info versions 2 and 3. This allows an attacker controlling a Ceph monitor or an on-path attacker on an unsigned/unencrypted messenger session to cause an out-of-bounds read in the CephFS client kernel. The issue is mitigated by adding a ceph_decode_need() check for the export-targets array for all info versions >= 2 and by safely computing the byte count to prevent integer overflow. The flaw leads to a kernel slab-out-of-bounds read but does not leak information to the attacker.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 13:03 UTC

Technical details

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