Information Exposure 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-20537017
- published6 Oct 2026
- disclosed2 Oct 2026
Introduced: 2 Oct 2026
NewCVE-2026-63573 (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 Information Exposure via the KeyTransRecipientInformation.UnwrapKey path in CMS. An attacker can recover a captured EnvelopedData message’s content-encryption key, and then its content, by submitting many modified ciphertexts to an application that decrypts them with the recipient’s RSA private key and reveals how unwrap failed. When the RSA-encrypted CEK has invalid PKCS#1 v1.5 padding, UnwrapKey returns a distinct “bad padding in message.” CmsException instead of blending the failure into a random-key result, so invalid ciphertexts are distinguishable from correctly padded ones that only fail later during content decryption.