PatchTheCVECVE-2026-63567: Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc
CVE-2026-63567 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.
Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has captured an IES or ECIES ciphertext, and who can submit modified ciphertexts for decryption under the same key pair, to recover its plaintext via a CBC padding-oracle attack, because in block-cipher mode the engine decrypts the ciphertext and removes its padding before verifying the MAC. A padding failure is
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 | 0.5% (top 60%) |
| CISA exploited list | No |
| Weakness | CWE-203 |
| 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-2026-63567?
bc-csharp: upgrade to 2.7.0. Exact commands for each OS are on this page.
Is CVE-2026-63567 being exploited?
CVE-2026-63567 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-2026-63567 affect?
CVE-2026-63567 affects bc-csharp. Severity is high (CVSS 7.5). Observable discrepancy in IesEngine.DecryptBlock in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who has captured an IES or ECIES ciphertext, and who can submit modified ciphertexts for decryption under t
How urgent is CVE-2026-63567?
Priority 41/100. High severity; Remotely exploitable, no login, no user action
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