In Apache httpd before 2.2.34 and 2.4.x before 2.4.27 the value placeholder in Proxy-Authorization headers of type 'Digest' was not initialized or reset before or between successive key=value assignments by mod_auth_digest. Providing an initial key with no '=' assignment could reflect the stale value of uninitialized pool memory used by the prior request leading to leakage of potentially confidential information and a segfault in other cases resulting in denial of service.