🛡️ GHSA-gmhj-xjfh-cf6m — caddy-ssh

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-287 OSV
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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](https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L&version=3.1)

Root Cause Analysis

In this case, in the following PAM transaction, only a call to pam.Authenticate is used to login a user.

https://github.com/mohammed90/caddy-ssh/blob/1d980ceea6e67765daf19b5e644c7a0773fdaa13/internal/authentication/os/pam.go#L60

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

  • [Man Page for pam_acct_mgmt](https://man7.org/linux/man-pages/man3/pam_acct_mgmt.3.html)
  • [CWE-863](http://cwe.mitre.org/data/definitions/863.html)
  • [CWE-285](http://cwe.mitre.org/data/definitions/285.html)

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs administrative privileges on the target. No user interaction is required. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity high, availability none.

Weakness class

GHSA-gmhj-xjfh-cf6m is classified as CWE-287: Improper Authentication. The identity of the caller is not established correctly, so an attacker can act as another user.

Affected software

GHSA-gmhj-xjfh-cf6m is recorded against 1 package.

  • github.com/mohammed90/caddy-ssh

Timeline and source

Published on 23 September 2022. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
github.com (Web)
github.com (Package)

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N
CWE CWE-287
Public Exploit ✅ No
Source OSV
Published 2022-09-23
Updated 2026-08-20
Modified 2022-09-23
Fix URL N/A

Affected Packages

Software From version Fixed in
github.com/mohammed90/caddy-ssh — —

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