In March 2017, a serious flaw was discovered in many popular implementations of JWE, the [[Elliptic-curve cryptography#Invalid curve attack|invalid curve attack]].<ref>{{Cite news|url=https://www.infoworld.com/article/3184582/security/critical-flaw-alert-stop-using-json-encryption.html|title=Critical flaw alert! Stop using JSON encryption|last=Rashid|first=Fahmida|date=27 March 2017|work=InfoWorld|access-date=8 June 2018}}</ref>
One implementation of an early (pre-finalisedfinalized) version of JWE also suffered from [[Bleichenbacher’s attack]].<ref>{{Citation|last=Jager|first=Tibor|title=Bleichenbacher's Attack Strikes again: Breaking PKCS#1 v1.5 in XML Encryption|date=2012|last2=Schinzel|last3=Somorovsky|first2=Sebastian|first3=Juraj|work=Computer Security – ESORICS 2012|pages=752–769|publisher=Springer Berlin Heidelberg|language=en|doi=10.1007/978-3-642-33167-1_43|isbn=9783642331664|citeseerx=10.1.1.696.5641|quote=Beyond XML Encryption, the recent JSON Web Encryption (JWE) specification prescribes PKCS#1 v1.5 as a mandatory cipher. This specification is under development and at the time of writing there existed only one implementation following this specification. We verified that this implementation was vulnerable to two versions of the Bleichenbacher’s attack: the direct attack based on error messages and the timing-based attack.}}</ref>
