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Vulnerabilities

Vulnerability · CVE-2026-71884

Reusing a Nonce, Key Pair in Encryption

Published Oct 9, 2026 · catalog updated Oct 15, 2026 · Reusing a Nonce, Key

Check if you run it

No confirmed exploitation is on record for CVE-2026-71884. EPSS is 0.41%. Act only if a listed version of Reusing a Nonce, Key is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Reusing a Nonce, Key).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.2
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.41%
Remediation
Not established
Affected products
maven org.bouncycastle:bcprov-debug-lts8on · maven org.bouncycastle:bcprov-lts8on

In Bouncy Castle for Java LTS before 2.73.13, the native one-shot CTR packet cipher did not check that the requested input length fitted the counter space the IV left. In CTR mode the IV and the block counter share one 16-byte block, so an IV of 13 to 15 bytes leaves a counter of only 1 to 3 bytes, addressing 256, 65536 or 16777216 blocks respectively. Given a longer input the counter wrapped and the keystream repeated from the start of the same packet, and the call then returned the full input length as though every byte had been correctly transformed. Two segments of the message were therefore encrypted under the same keystream, so their plaintexts can be recovered from the ciphertext alone, without the key, while the caller saw neither an exception nor a short length to indicate it. The streaming implementation validates at init and again while processing, and the portable AESCTRPacketCipher rejects such a request with "Counter in CTR/SIC mode out of range.", but the native one-shot path has a single entry point and performed no counter-range validation there. It now preflights the IV-derived counter range and rejects an over-long request before any output is written, so the operation is failure-atomic and never reports success for bytes it did not correctly transform. A counter of four bytes or more cannot be exhausted by a Java int length and is unaffected, as is a full 16-byte IV, where the counter range is the caller's responsibility. Bouncy Castle for Java (bcprov) is not affected, as it ships no native implementations.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • maven org.bouncycastle:bcprov-debug-lts8onversion unspecified
  • maven org.bouncycastle:bcprov-lts8onversion unspecified

How to fix CVE-2026-71884

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-71884. EPSS is 0.41%. Act only if a listed version of Reusing a Nonce, Key is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-323. EPSS 0.41%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 14, 2026 · Snyk Vulnerability Database

    Detected

    Reusing a Nonce, Key Pair in Encryption

  2. Oct 15, 2026 · NIST NVD

    Updated

    In Bouncy Castle for Java LTS before 2.73.13, the native one-shot CTR packet cipher did not check that the requested input length fitted the counter space the IV left. In CTR mode the IV and the block counter share one 16-byte block, so an IV of 13 to 15 bytes leaves a counter of only 1 to 3 bytes, addressing 256, 65536 or 16777216 blocks respectively. Given a longer input the counter wrapped and

Sources

  • CVE.orgVulnerability recordCVE-2026-71884

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-71884

    30-day exploitation probability 0.4%

    first.org
  • NIST NVDVulnerability recordCVE-2026-71884

    In Bouncy Castle for Java LTS before 2.73.13, the native one-shot CTR packet cipher did not check that the requested input length fitted the counter space the IV left. In CTR mode the IV and the block counter share one 16-byte block, so an IV of 13 to 15 bytes leaves a counter of

    nvd.nist.gov
  • Snyk Vulnerability DatabasePackage advisorySNYK-JAVA-ORGBOUNCYCASTLE-20828170

    Reusing a Nonce, Key Pair in Encryption

    security.snyk.io
  • Snyk Vulnerability DatabasePackage advisorySNYK-JAVA-ORGBOUNCYCASTLE-20828171

    Reusing a Nonce, Key Pair in Encryption

    security.snyk.io

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.