CVE-2025-61911: python-ldap has sanitization bypass in ldap.filter.escape_filter_chars

Summary The sanitization method ldap.filter.escapefilterchars can be tricked to skip escaping of special characters when a crafted list or dict is supplied as the assertionvalue parameter, and the non-default escapemode=1 is configured.

Details The method ldap.filter.escapefilterchars supports 3 different escaping modes. escapemode=0 (default) and escapemode=2 happen to raise exceptions when a list or dict object is supplied as the assertionvalue parameter. However, escapemode=1 happily computes without performing adequate logic to ensure a fully escaped return value.

PoC >>> import ldap.filter Exploitable >>> ldap.filter.escapefilterchars(["abc@()/xyz"], escapemode=1) 'abc@()/xyz' >>> ldap.filter.escapefilterchars({"abc@()/xyz": 1}, escapemode=1) 'abc@()/xyz' Not exploitable >>> ldap.filter.escapefilterchars("abc@()/xyz", escapemode=1) 'abc@\\2a\\28\\29\\2fxyz' >>> ldap.filter.escapefilterchars(["abc@()/xyz"], escapemode=0) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib64/python3.12/site-packages/ldap/filter.py", line 41, in escapefilterchars s = assertionvalue.replace('\\', r'\5c') ^^^^^^^^^^^^^^^^^^^^^^^ AttributeError: 'list' object has no attribute 'replace' >>> ldap.filter.escapefilterchars(["abc@()/xyz"], escapemode=2) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib64/python3.12/site-packages/ldap/filter.py", line 36, in escapefilterchars r.append("\\%02x" % ord(c)) ^^^^^^ TypeError: ord() expected a character, but string of length 11 found Impact If an application relies on the vulnerable method in the python-ldap library to escape untrusted user input, an attacker might be able to abuse the vulnerability to launch ldap injection attacks which could potentially disclose or manipulate ldap data meant to be inaccessible to them.

With Python being a dynamically typed language, and the commonly used JSON format supporting list and dict, it is to be expected that Python applications may commonly forward unchecked and potentially malicious list and dict objects to the vulnerable sanitization method.

The vulnerable escapemode=1 configuration does not appear to be widely used.

Suggested Fix Add a type check at the start of the ldap.filter.escapefilterchars method to raise an exception when the supplied assertionvalue parameter is not of type str.