Native AES packet cipher returns the raw AES key on an alias

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.

Scores

EPSS (exploitation in 30 days)

0.25% · top 83% of all CVEs (6 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.2.

Weakness

• CWE-200 Exposure of Sensitive Information to an Unauthorized Actor (opens in a new tab)All about CWE-200 and its CVEs

Affected products

• Legion of the Bouncy Castle Inc. · BC-LTS-JAVA

  • affected 2.73.4 – < 2.73.13

References (1)

• https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071883 (opens in a new tab)vendor-advisory

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-71883](https://trackcve.app/badge/CVE-2026-71883.svg)](https://trackcve.app/cve/CVE-2026-71883)

Record last updated 5 Oct 2026, 16:05 UTC.