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Security Advisories: GSA_kwCzR0hTQS1nbWhqLXhqZmgtY2Y2bc4AAvAc
Caddy-SSH vulnerable to Authorization Bypass due to incorrect usage of PAM library
Not invoking a call to pam_acct_mgmt
after a call to pam_authenticate
to check the validity of a login can lead to an authorization bypass.
Impact
Exploitability
The attack can be carried over the network. A complex non-standard configuration or a specialized condition is required for the attack to be successfully conducted. The attacker also requires access to a users credentials, be it expired, for an attack to be successful. There is no user interaction required for successful execution. The attack can affect components outside the scope of the target module.
Impact
Using this attack vector, an attacker may access otherwise restricted parts of the system. The attack can be used to gain access to confidential files like passwords, login credentials and other secrets. Hence, it has a high impact on confidentiality. It may also be directly used to affect a change on a system resource. Hence has a medium to high impact on integrity. This attack may not be used to affect the availability of the system. Taking this account an appropriate CVSS v3.1 vector would be
AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
Root Cause Analysis
In this case, in the following PAM transaction, only a call to pam.Authenticate
is used to login a user.
This implies that a user with expired credentials can still login.
The bug can be verified easily by creating a new user account, expiring it with chage -E0 <username>
and then trying to log in with the expired credentials.
Patches
This can be fixed by invoking a call to pam.AcctMgmt
after a successful call to pam.Authenticate
References Permalink: https://github.com/advisories/GHSA-gmhj-xjfh-cf6m
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS1nbWhqLXhqZmgtY2Y2bc4AAvAc
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: over 1 year ago
Updated: over 1 year ago
CVSS Score: 7.7
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N
Identifiers: GHSA-gmhj-xjfh-cf6m
References:
- https://github.com/mohammed90/caddy-ssh/security/advisories/GHSA-gmhj-xjfh-cf6m
- https://github.com/mohammed90/caddy-ssh/commit/4b3e639d64c55f91152ffb51a4af35a8845c95a3
- https://github.com/advisories/GHSA-gmhj-xjfh-cf6m
Blast Radius: 1.0
Affected Packages
go:github.com/mohammed90/caddy-ssh
Dependent packages: 0Dependent repositories: 0
Downloads:
Affected Version Ranges: = 0.0.1
No known fixed version
All affected versions: 0.0.1