Improper Verification of Cryptographic Signature Affecting org.bouncycastle:bcpg-jdk18on package, versions [1.81,1.86)
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 Oct 2026
- disclosed3 Oct 2026
- creditArpan Sharma
Introduced: 3 Oct 2026
NewCVE-2026-71887 (opens in a new tab)How to fix?
Upgrade org.bouncycastle:bcpg-jdk18on to version 1.86 or higher.
Overview
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature through OpenPGPCertificate.getApplyingSubpacket() in org.bouncycastle.openpgp.api. An attacker can make a genuine signature from a victim’s signing subkey validate under an attacker-controlled certificate by supplying a Subkey Binding signature that omits the subkey’s Key Flags and omits the embedded Primary Key Binding signature. The flaw lets a subkey inherit signing capability from the primary key’s certificate-wide Key Flags even when its own binding signature does not grant that capability, so OpenPGPSignature.OpenPGPDocumentSignature.isValid() can report the victim’s signature as valid and attribute it to the attacker’s certificate. For relying parties, this breaks signature attribution and causes authentic signed messages to be accepted under the wrong identity.