In the Bouncy Castle JCE Provider version 1.55 and earlier ECDSA does not fully validate ASN.1 encoding of signature on verification. It is possible to inject extra elements in the sequence making up the signature and still have it validate, which in some cases may allow the introduction of 'invisible' data into a signed structure.
Upstream patch:
https://github.com/bcgit/bc-java/commit/843c2e60f67d71faf81d236f448ebbe56c62c647#diff-25c3c78db788365f36839b3f2d3016b9
In the Bouncy Castle JCE Provider versions 1.51 to 1.55, a carry propagation bug was introduced in the implementation of squaring for several raw math classes have been fixed (org.bouncycastle.math.raw.Nat???). These classes are used by our custom elliptic curve implementations (org.bouncycastle.math.ec.custom.), so there was the possibility of rare (in general usage) spurious calculations for elliptic curve scalar multiplications. Such errors would have been detected with high probability by the output validation for our scalar multipliers.
Bouncy Castle JCE Provider could provide weaker than expected security, caused by a flaw in the DSA signature generation. A remote attacker could exploit this vulnerability to launch timing attacks.
Bouncy Castle JCE Provider could allow a remote attacker to obtain sensitive information, caused by a flaw in the other party DH public key. A remote attacker could exploit this vulnerability to reveal details via invalid keys.
Bouncy Castle JCE Provider could provide weaker than expected security, caused by a flaw in the DSA key pair generator. A remote attacker could exploit this vulnerability to launch further attacks.
Bouncy Castle JCE Provider could provide weaker than expected security, caused by an environment where timings can be easily observed. A remote attacker could exploit this vulnerability to conduct a padding oracle attack.
Bouncy Castle JCE Provider could allow a remote attacker to obtain sensitive information, caused by a flaw in the AESEngine. An attacker could exploit this vulnerability to obtain sensitive information.