VulnerabilityPublished 28 Oct 2026

CVE-2026-109411: An access control bypass flaw was found in Samba's vfs_ceph_rgw module in it's openat() function

Source GCVE Database

Authoritative record:CVE-2026-109411· High 8.1

Not known to be exploited · CVSS 8.1 High : upgrade to 4.25.1 soon.

Data as of 28 Oct 2026, 22:13 UTC

CVSS 3.1 base score

8.1High

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

Patch: Available – fixed in 4.25.1

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

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

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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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.

ghsa-pwp9-3h93-h2x8

What to do

Upgrade Samba to 4.25.1.

Affected software

Product	Affected	Fixed in
Sambasamba	Affected >=4.25.0 <4.25.1	Fixed in 4.25.1

AI-suggested

To mitigate this vulnerability, disable the experimental vfs_ceph_rgw module on any Samba shares by removing 'ceph_rgw' from the 'vfs objects' setting in /etc/samba/smb.conf and then reload the Samba service (systemctl reload smb). Note that reloading may briefly interrupt active sessions and disables Ceph RGW integration for those shares. Alternatively, setting 'case sensitive = yes' on affected shares prevents the vulnerability by treating differently-cased filenames as distinct objects, though this changes share behavior for clients relying on case-insensitive handling. Red Hat's Samba packages do not include this module and are not affected, so no action is required for those users.

Description

CVE-2026-109411 is an access control bypass vulnerability in Samba's experimental vfs_ceph_rgw module affecting its openat() function. Authenticated users can bypass access controls to read or overwrite restricted files on shares configured with this module due to improper case-insensitive filename handling. This causes the server to treat existing files as new, skipping permission checks. The vulnerability is limited to Samba deployments using this experimental S3-to-SMB gateway feature introduced in Samba 4.25. Red Hat's Samba packages do not include this module, so they are not affected. Mitigation involves disabling the vfs_ceph_rgw module or enabling case-sensitive file handling on affected shares.

Impact

The vulnerability allows an authenticated user to bypass access controls on Samba shares configured with the experimental vfs_ceph_rgw module, enabling unauthorized reading or overwriting of restricted files. This compromises confidentiality and integrity of data on affected shares. The impact is high due to the ability to access sensitive data owned by other users without proper permission checks. Availability is not affected. The flaw is limited to Samba deployments using this experimental module and does not affect standard Samba or Red Hat distributions.

CWE-178Improper Handling of Case Sensitivity (opens in a new tab)
Base weakness
The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.
Architecture and Design · Input Validation
Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Oct 2026, 22:13 UTC

WeaknessesCWE-178

Technical details

References

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