PatchTheCVECVE-2026-16001: Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (a
CVE-2026-16001 is a high-severity flaw (CVSS 7.5) affecting bc-csharp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has observed one encrypted message with known plaintext to forge shorter messages of their choosing that the recipient accepts as authentic, via a crafted ciphertext and MAC tag, because the MAC key was t
Why this priority
- High severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.2% (top 91%) |
| CISA exploited list | No |
| Weakness | CWE-354 |
| Published | 2026-10-02 |
| Last modified | 2026-10-27 |
Last updated 2026-10-27 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-16001?
bc-csharp: upgrade to 2.7.0. Exact commands for each OS are on this page.
Is CVE-2026-16001 being exploited?
CVE-2026-16001 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-16001 affect?
CVE-2026-16001 affects bc-csharp. Severity is high (CVSS 7.5). Exposure of the message authentication key through the encryption keystream in the stream mode of IesEngine (an IesEngine constructed without a block cipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacke
How urgent is CVE-2026-16001?
Priority 33/100. High severity; Remotely exploitable, no login, no user action
Related CVEs
- CVE-2026-15999 HIGH 7.5 UPGRADE Improper validation of integrity check value in the AES-CCM implementation (CcmParameters and CcmBlockCipher)
- CVE-2026-16000 HIGH 7.5 UPGRADE Missing cryptographic step in the DSTU 7624 CCM mode implementation (KCcmBlockCipher) in Legion of the Bouncy
- CVE-2026-63566 HIGH 7.5 UPGRADE Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReass
- CVE-2026-63567 HIGH 7.5 UPGRADE Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc
- CVE-2026-63568 HIGH 7.5 UPGRADE Allocation of resources without limits or throttling in the CMP/CRMF password-based MAC verifier (PKMacBuilder