High

OpenPGP AEAD Final-Tag Validation Bypass in Bouncy Castle Java

IdentifiersCVE-2026-12817CWE-354· Improper Validation of Integrity…

CVE-2026-12817 is an integrity-validation flaw in Bouncy Castle Java OpenPGP AEAD decryption. When ciphertext data is aligned to an AEAD chunk boundary, decryption skips validation of the final authentication tag. The issue affects Bouncy Castle for Java before 1.85, Bouncy Castle for Java LTS before 2.73.12, and BC-FJA bcpg-fips releases before 1.0.13 in the 1.0.x series, 2.0.13 in the 2.0.x series, and 2.1.13 in the 2.1.x series.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

An attacker able to modify chunk-aligned OpenPGP AEAD ciphertext may tamper with encrypted data without the final authentication tag being checked. This undermines the integrity and authentication assurances expected from AEAD-protected OpenPGP content.

Mitigation

If you can’t patch tonight, do this now.

Until patched versions are deployed, do not process untrusted or attacker-modifiable OpenPGP AEAD ciphertext using affected Bouncy Castle versions. Where feasible, use an alternate implementation or independently authenticate encrypted data before accepting decrypted content.

Remediation

Patch, then assume compromise.

Upgrade Bouncy Castle for Java to version 1.85 or later, Bouncy Castle for Java LTS to version 2.73.12 or later, and BC-FJA bcpg-fips to version 1.0.13 or later for the 1.0.x series, 2.0.13 or later for the 2.0.x series, or 2.1.13 or later for the 2.1.x series.

PUBLIC EXPLOITS

Exploits

No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.

VALID 0 / 1 TOTALView more in app

All candidate exploits were filtered out by Mallory's validation.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Bouncy CastleBc-Javaapplication

Bouncy CastleBcpg-Fipsapplication

Bouncy CastleBouncy Castleapplication

Bouncy CastleBouncy Castle For Javaapplication

Bouncy CastleBouncy Castle For Java Ltsapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

4 SOURCESView more in app

ghsa syntheticNews

Aug 3, 2026

GHSA-9q38-7pr7-8j6w

An OpenPGP AEAD decryption flaw in Bouncy Castle for Java whereby decryption skips final-tag verification for chunk-aligned data, affecting versions before the stated fixed releases.

cvefeed high severityNews

Aug 3, 2026

CVE-2026-12817 - OpenPGP AEAD decryption skips final tag on chunk-aligned data

An integrity-validation flaw in Bouncy Castle OpenPGP AEAD decryption where the final authentication tag is skipped on chunk-aligned data, affecting Bouncy Castle for Java, Java LTS, and Java FIPS variants.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity1