Lemur manages TLS certificate creation. Prior to 1.9.0, when LDAP TLS is enabled (LDAP_USE_TLS = True), Lemur's LDAP authentication module unconditionally disables TLS certificate verification at the global ldap module level. This allows a man-in-the-middle attacker positioned between Lemur and the LDAP server to intercept all authentication credentials. This vulnerability is fixed in 1.9.0.

Affected: PyPI: lemur

## Description

### Overview

When LDAP TLS is enabled (`LDAP_USE_TLS = True`), Lemur's LDAP authentication module unconditionally disables TLS certificate verification at the **global** `ldap` module level. This allows a man-in-the-middle attacker positioned between Lemur and the LDAP server to intercept all authentication credentials.

### Vulnerable Code

**Location:** `lemur/auth/ldap.py`, `_bind()` method, line ~172

```python if self.ldap_use_tls: ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, ldap.OPT_X_TLS_NEVER) ```

Key issues:

1. `ldap.set_option()` is a **global** call (as opposed to `self.ldap_client.set_option()`), meaning it disables TLS verification for the entire Python process, not just this connection 2. `OPT_X_TLS_NEVER` means no certificate validation is performed whatsoever — self-signed, expired, wrong hostname, and revoked certificates are all silently accepted 3. There is no configuration option to override this behavior — TLS verification is always disabled when TLS is enabled

### Impact

A network-positioned attacker (man-in-the-middle) between Lemur and the LDAP server can:

- **Intercept all LDAP credentials** (usernames and plaintext passwords) for every user who authenticates - **Modify LDAP responses** to inject arbitrary group memberships, granting admin access - **Compromise the entire PKI infrastructure** managed by Lemur, since authentication controls access to certificates and private keys

This is particularly severe because Lemur is…

Affected: PyPI: lemur

## Description

### Overview

When LDAP TLS is enabled (`LDAP_USE_TLS = True`), Lemur's LDAP authentication module unconditionally disables TLS certificate verification at the **global** `ldap` module level. This allows a man-in-the-middle attacker positioned between Lemur and the LDAP server to intercept all authentication credentials.

### Vulnerable Code

**Location:** `lemur/auth/ldap.py`, `_bind()` method, line ~172

```python if self.ldap_use_tls: ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, ldap.OPT_X_TLS_NEVER) ```

Key issues:

1. `ldap.set_option()` is a **global** call (as opposed to `self.ldap_client.set_option()`), meaning it disables TLS verification for the entire Python process, not just this connection 2. `OPT_X_TLS_NEVER` means no certificate validation is performed whatsoever — self-signed, expired, wrong hostname, and revoked certificates are all silently accepted 3. There is no configuration option to override this behavior — TLS verification is always disabled when TLS is enabled

### Impact

A network-positioned attacker (man-in-the-middle) between Lemur and the LDAP server can:

- **Intercept all LDAP credentials** (usernames and plaintext passwords) for every user who authenticates - **Modify LDAP responses** to inject arbitrary group memberships, granting admin access - **Compromise the entire PKI infrastructure** managed by Lemur, since authentication controls access to certificates and private keys

This is particularly severe because Lemur is…