VulnerabilityPublished 11 Nov 2026

CVE-2026-64666: mcdope pam_usb · Reliance on Untrusted Inputs in a Security Decision

Affects mcdope pam_usbSource CVE Database V5

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Not known to be exploited · CVSS 7.1 High : upgrade to 0.9.3 soon.

Data as of 11 Nov 2026, 04:04 UTC

CVSS 3.1 base score

7.1High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	7.1

Patch: Available – fixed in 0.9.3

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

Attack Vector: Local
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: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
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 11 Nov 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 10 Nov 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 mcdope pam_usb to 0.9.3.

Affected software

Product	Affected	Fixed in
mcdopepam_usb	Affected <0.9.3	Fixed in 0.9.3

AI-suggested

Upgrade pam_usb to version 0.9.3 or later, where this vulnerability is patched. No additional mitigation is required once the update is applied.

Description

A vulnerability in pam_usb prior to version 0.9.3 allows an attacker to bypass the XRDP session denial rule by manipulating the XRDP_SESSION environment variable. This occurs because pam_usb uses the insecure getenv(3) function instead of secure_getenv(3) to read XRDP_SESSION, enabling environment-based detection to be defeated. The issue is fixed in version 0.9.3.

Impact

An attacker with local privileges can bypass the XRDP session denial rule by manipulating the environment variable XRDP_SESSION, potentially allowing unauthorized access or authentication bypass in systems using pam_usb for hardware authentication. The confidentiality and integrity of the authentication process are impacted, but availability is not affected.

Summary

pam_usb, a hardware authentication module for Linux using removable media, improperly reads the XRDP_SESSION environment variable using getenv(3) instead of secure_getenv(3) in versions before 0.9.3. Since pam_usb.so can be loaded into a setuid PAM host where the calling user controls the environment, an attacker can clear XRDP_SESSION before invoking the host to bypass the explicit XRDP-deny rule. Although other remote session detection mechanisms remain, the environment-based detection is circumvented. This vulnerability is addressed in pam_usb version 0.9.3.

CWE-807Reliance on Untrusted Inputs in a Security Decision (opens in a new tab)
Base weaknessLikelihood of exploit: HighOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.
Architecture and Design · Attack Surface Reduction
Store state information and sensitive data on the server side only.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
OWASP Cheat Sheets
Secure Design Principles (opens in a new tab)
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 11 Nov 2026, 04:04 UTC

WeaknessesCWE-807

Technical details

References

Community reviews

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