Improper Input Validation Affecting bouncycastle.cryptography package, versions [,2.7.0)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-DOTNET-BOUNCYCASTLECRYPTOGRAPHY-20537027
- published6 Oct 2026
- disclosed2 Oct 2026
Introduced: 2 Oct 2026
NewCVE-2026-63569 (opens in a new tab)How to fix?
Upgrade BouncyCastle.Cryptography to version 2.7.0 or higher.
Overview
Affected versions of this package are vulnerable to Improper Input Validation through DHAgreement.CalculateAgreement in crypto/src/crypto/agreement/DHAgreement.cs. An attacker can make the local party compute a shared value the attacker already knows, or expose the static private key modulo small factors of p - 1, by supplying a crafted out-of-range or small-order ephemeral Diffie-Hellman value. This breaks MTI/A0 key authentication for applications that call DHAgreement directly, allowing an on-path attacker or malicious peer to defeat the expected secrecy of the agreement.