CVE-2026-12860
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn Bouncy Castle for Java before 1.85, RSA PKCS#1 verification skips last two hash bytes in NULL-omitted path. This issue also affects Bouncy Castle for Java LTS before 2.73.12.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIn Bouncy Castle for Java before version 1.85 (and LTS before 2.73.12), the RSA PKCS#1 signature verification implementation contains a flaw where it skips validation of the last two hash bytes when processing signatures with omitted NULL parameters. This allows attackers to potentially forge valid RSA signatures by manipulating the hash value's trailing bytes.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- Authentication
- X
- User interaction
- None
- Scope
- X
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Bouncy Castle Java library versionLocate the bcprov*.jar file and check its version in the filename, MANIFEST.MF file, or in your project's dependency management (pom.xml, build.gradle). Also check package org.bouncycastle for the version constant.Affected if The installed version is earlier than 1.85 (non-LTS) or earlier than 2.73.12 (LTS line)
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Locate RSA PKCS#1 signature verification codeSearch your codebase for uses of java.security.Signature, BouncyCastle's SignerInterface, or the 'RSA' algorithm in signature verification contexts, especially calls to verify() methods.Affected if Your code performs RSA PKCS#1 signature verification using Bouncy Castle
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Check for NULL-omitted algorithm identifier usageReview signature verification code to determine if it uses RSA PKCS#1 v1.5 padding with NULL-omitted algorithm identifiers (OID). This is typically the default or common configuration in many signature verification implementations.Affected if The signature verification implementation uses the NULL-omitted algorithm identifier path (the vulnerable code path)
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Verify hash truncation behaviorTest your signature verification with known valid RSA PKCS#1 signatures. The vulnerability causes last 2 bytes of the hash to be ignored during verification, potentially accepting signatures that would normally be rejected.Affected if Signatures that should fail verification (e.g., with truncated or malformed hash endings) are incorrectly accepted
You are affected if you use a Bouncy Castle for Java version before 1.85 (or before LTS 2.73.12) AND your code performs RSA PKCS#1 signature verification using the NULL-omitted algorithm identifier path.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade Bouncy Castle Java to version 1.85 or later, or LTS version 2.73.12 or later. Alternatively, avoid using RSA PKCS#1 with NULL-omitted parameters until the upgrade is applied.
Bouncy Castle Java 1.85+ or LTS 2.73.12+
- 1. Identify the current Bouncy Castle for Java version in your project (check pom.xml, build.gradle, or dependency management)
- 2. For non-LTS users: Upgrade to version 1.85 or later (e.g., org.bouncycastle:bcprov-jdk18on version 1.85 or higher)
- 3. For LTS users: Upgrade to version 2.73.12 or later (e.g., org.bouncycastle:bcprov-jdk18on version 2.73.12 or higher)
- 4. Rebuild and test your application to verify the upgrade does not introduce regressions
- 5. If using a package manager (Maven/Gradle), run 'mvn dependency:tree' or 'gradle dependencies' to confirm the correct version is resolved
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation3.0 h
- Testing8.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,928.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-12860 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-12860 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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