Clarification: The first line in this CVE [1] was a copy&paste error
during message composition and is not part of the CVE.  This line can
make it sound as if CVE-2016-5019 is only an information disclosure
vulnerability rather than a deserialization attack vector.  I
apologize for the confusion.

--- Original Advisory ---
CVE-2016-5019 Apache MyFaces Trinidad information disclosure vulnerability

Severity: Important

Vendor:
The Apache Software Foundation

Versions Affected:
Trinidad from 1.0.0 to 1.0.13
Trinidad from 1.2.1 to 1.2.14
Trinidad from 2.0.0 to 2.0.1
Trinidad from 2.1.0 to 2.1.1

Description:

Trinidadas CoreResponseStateManager both reads and writes view state strings using ObjectInputStream/ObjectOutputStream directly.  By doing so, Trinidad bypasses the view state security features provided by the JSF implementations - ie. the view state is not encrypted and is not MACaed.  

Trinidadas CoreResponseStateManager will blindly deserialize untrusted view state strings, which makes Trinidad-based applications vulnerable to deserialization attacks.

Mitigation:

All users of Apache Trinidad should upgrade to either 2.1.2, 2.0.2, or 1.2.15 and enable view state encryption using org.apache.myfaces.USE_ENCRYPTION and related web configuration parameters.

See http://wiki.apache.org/myfaces/Secure_Your_Application for details.

Upgrading all Commons Collections jars on the class path to 3.2.2/4.1 will prevent certain well-known vectors of attack, but will not entirely resolve this issue.

References:
https://issues.apache.org/jira/browse/TRINIDAD-2542

This issue was discovered by Teemu KA$?A$?riA$?inen and reported by Andy Schwartz