Improper Verification of Cryptographic Signature Affecting org.bouncycastle:bcprov-jdk18on package, versions [,1.85)
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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- published4 Aug 2026
- disclosed3 Aug 2026
- creditUnknown
Introduced: 3 Aug 2026
NewCVE-2026-12860 (opens in a new tab)How to fix?
Upgrade org.bouncycastle:bcprov-jdk18on to version 1.85 or higher.
Overview
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature in the verifySignature() method of RSADigestSigner, whose legacy NULL-omitted DigestInfo path computes comparison offsets as length - hash.length - 2, so its two comparison loops jointly cover only bytes [0..sig.length-2) and leave the final two hash bytes unverified. An attacker can forge an RSA PKCS#1 signature by producing a message whose digest matches the signed digest in every byte except the last two, reducing the second-preimage work factor by 2^16. The flawed path is reachable by default only for signatures using NULL-less DigestInfo encoding, across BC-lightweight TLS rsa_pkcs1_*, PKIX/CMS, and OpenPGP RSA verification, and only when org.bouncycastle.pkcs1.strict_digestinfo is not set.
Workaround
This vulnerability can be avoided by setting the system property org.bouncycastle.pkcs1.strict_digestinfo, which enforces strict DigestInfo parsing and rejects the NULL-omitted encoding that reaches the flawed path.