CVE-2017-9788: Uninitialized memory reflection in mod_auth_digest

Severity: Important

Vendor: The Apache Software Foundation

Versions Affected:
all versions through 2.2.33 and 2.4.26

Description:
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

Mitigation:
All users of httpd should upgrade to 2.4.27 (or minimally
2.2.34, which will receive no further security releases.)
Alternately, the administrator could configure httpd to
reject requests with a header matching a complex regular
expression identifing where = character does not occur
in the first key=value pair, as in the following syntax;
[Proxy-]Authorization: Digest key[,key=value]

Credit:
The Apache HTTP Server security team would like to thank Robert AwiAcki
for reporting this issue.

References:
https://httpd.apache.org/security_report.html