CVE-2026-71883 Native AES packet cipher returns the raw AES key on an alias
An attacker can obtain the raw AES key if an application encrypts data in place over the key array, due to incorrect JNI memory release in native ciphers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-71883?
CVE-2026-71883 is a high-severity vulnerability in Legion of the Bouncy Castle Inc. BC-LTS-JAVA, published on 3 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In Bouncy Castle for Java LTS before 2.73.13, the one-shot native packet ciphers for AES-CBC, CCM, CFB, CTR, GCM and GCM-SIV released the caller's key, IV and additional authenticated data arrays with JNI's ReleaseByteArrayElements in mode 0, which commits the native copy back into the Java array. Those arrays are read-only to the native code, and on a JVM that returns a copy rather than a pin the copy still holds the input bytes as they were read. The output buffer is taken through a separate critical region and committed first, so where an application passed the same Java array as both an input and the destination - encrypting in place over KeyParameter.getKey(), for example - the later mode-0 release of the key wrote the unchanged key bytes over the ciphertext that had just been produced. The call still returned the correct output length, so an application encrypting in place over its own key array was handed the raw AES key where it expected ciphertext, with nothing in the API to indicate it, and would transmit or store the key in place of the message. The read-only input arrays are now released with JNI_ABORT, freeing the native copy without copying it back, and mode 0 is reserved for arrays the native code wrote. The pure-Java packet ciphers and the streaming native modes are not affected. Bouncy Castle for Java (bcprov) is not affected, as it ships no native implementations.
Weakness: CWE-200
Which versions are affected by CVE-2026-71883?
How do I fix CVE-2026-71883?
No fix has been published for CVE-2026-71883 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-71883 being exploited?
There is no known exploitation of CVE-2026-71883 in the wild and no public exploit code.
Sources
Also known as GHSA-f5wg-4mfp-h458.