# GHSA-gmhj-xjfh-cf6m: Caddy-SSH vulnerable to Authorization Bypass due to incorrect usage of PAM library > Attackers with expired credentials can bypass authorization checks in Caddy-SSH to access restricted system resources and confidential data. - **Severity:** Not scored - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 23 Sep 2022 ## What is GHSA-gmhj-xjfh-cf6m? GHSA-gmhj-xjfh-cf6m is an authentication bypass vulnerability in github.com/mohammed90/caddy-ssh, published on 23 Sep 2022. Any signed-in user can exploit it over the network, with no action from the victim. ### Official description 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 ` 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) ## Which versions are affected by GHSA-gmhj-xjfh-cf6m? 2 open source packages ship an affected version, including github.com/mohammed90/caddy-ssh. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/mohammed90/caddy-ssh` | Go | All versions | None | | `github.com/mohammed90/caddy-ssh` | Go | All versions | None | ## How do I fix GHSA-gmhj-xjfh-cf6m? No fix has been published for GHSA-gmhj-xjfh-cf6m yet. Limit exposure of the affected software until one is available. ## Is GHSA-gmhj-xjfh-cf6m being exploited? There is no known exploitation of GHSA-gmhj-xjfh-cf6m in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for GHSA-gmhj-xjfh-cf6m and fix it if it is affected. What it is: GHSA-gmhj-xjfh-cf6m is an authentication bypass vulnerability in github.com/mohammed90/caddy-ssh, published on 23 Sep 2022. Any signed-in user can exploit it over the network, with no action from the victim. Exploitation: There is no known exploitation of GHSA-gmhj-xjfh-cf6m in the wild and no public exploit code. Affected packages and fixed versions: - github.com/mohammed90/caddy-ssh (Go): affected all versions; no fix listed - github.com/mohammed90/caddy-ssh (Go): affected all versions; no fix listed Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/GHSA-gmhj-xjfh-cf6m/ (Markdown: https://insights.sbomify.com/GHSA-gmhj-xjfh-cf6m/index.md) ``` ## Sources - OSV: https://osv.dev/vulnerability/GHSA-gmhj-xjfh-cf6m --- From sbomify Insights: https://insights.sbomify.com/GHSA-gmhj-xjfh-cf6m/ Summaries are generated and may contain mistakes; the official description above is the record.