asn1/cms/GCMParameters.java in the Bouncy Castle Crypto APIs 1.54 for Java, as used in Android 5.0.x before 5.0.2, 5.1.x before 5.1.1, and 6.x before 2016-04-01, has an improper AES-GCM-ICVlen value, which makes it easier for attackers to defeat a cryptographic protection mechanism and discover an authentication key via a crafted application, aka internal bug 26234568.

** DISPUTED ** The AES-GCM specification in RFC 5084, as used in Android 5.x and 6.x, recommends 12 octets for the aes-ICVlen parameter field, which might make it easier for attackers to defeat a cryptographic protection mechanism and discover an authentication key via a crafted application, aka internal bug 26234568.  NOTE: The vendor disputes the existence of this potential issue in Android, stating "This CVE was raised in error: it referred to the authentication tag size in GCM, whose default according to ASN.1 encoding (12 bytes) can lead to vulnerabilities. After careful consideration, it was decided that the insecure default value of 12 bytes was a default only for the encoding and not default anywhere else in Android, and hence no vulnerability existed."

https://android.googlesource.com/platform/external/bouncycastle/+/b3bddea0f33c0459293c6419569ad151b4a7b44b

https://android.googlesource.com/platform/libcore/+/efd369d996fd38c50a50ea0de8f20507253cb6de