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CVE-2026-71883

BC-LTS-JAVA: Native AES packet cipher returns the raw AES key on an alias

Legion of the Bouncy Castle Inc. BC-LTS-JAVA
CVSS
8.2High
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.25%Chance of exploitation activity in the next 30 days, higher than 15% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in2.73.13Fixed versionCVE List
Published3 Oct 2026Updated 5 Oct 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

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.

Text from CVE List

Affected versions 1

  • BC-LTS-JAVAaffected: 2.73.4 before 2.73.13CVE List

References 1