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Bouncy Castle Java EUVDEUVD-2026-52136

| CVE-2026-12817 HIGH
Improper Validation of Integrity Check Value (CWE-354)
2026-08-03 bcorg GHSA-9q38-7pr7-8j6w
Java Information Disclosure Bc Java Bc Lts Java Bc Fja Suse
8.7
CVSS 4.0 · Vendor: bcorg
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Severity by source

Vendor (bcorg) PRIMARY
8.7 HIGH
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
vuln.today AI
5.9 MEDIUM

Requires both ciphertext tamper access and a chunk-aligned plaintext, warranting AC:H; no authentication needed and no confidentiality or availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
SUSE
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Primary rating from Vendor (bcorg).

CVSS VectorVendor: bcorg

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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Source Code Evidence Fetched
Aug 03, 2026 - 04:24 vuln.today
Analysis Generated
Aug 03, 2026 - 04:24 vuln.today
CVE Published
Aug 03, 2026 - 02:54 cve.org
HIGH 8.7

DescriptionCVE.org

In Bouncy Castle for Java before 1.85, OpenPGP AEAD decryption skips final tag on chunk-aligned data. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpg-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).

AnalysisAI

OpenPGP AEAD decryption in Bouncy Castle for Java silently bypasses the final authentication tag when plaintext is an exact multiple of the AEAD chunk length, allowing an attacker who can tamper with ciphertext to strip trailing plaintext chunks and have the truncated message accepted as cryptographically authentic. Affected libraries span bc-java before 1.85, bc-lts-java before 2.73.12, and all three active BC-FJA FIPS series before their respective bcpg-fips 1.0.13, 2.0.13, and 2.1.13 releases. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Recon
Intercept or obtain write access to OpenPGP AEAD ciphertext
Delivery
Identify or induce chunk-aligned plaintext length
Exploit
Strip one or more trailing ciphertext chunks and the final authentication tag
Install
Adjust outer OpenPGP packet length to match truncated ciphertext
C2
Deliver tampered ciphertext to target application
Execute
Bouncy Castle AEAD stream processes surviving chunks, skips final tag, signals EOF
Impact
Application receives truncated plaintext silently accepted as authentic
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Vulnerability AssessmentAI

Exploitation Two concurrent conditions are required for exploitation. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The provided CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N) scores 8.7, reflecting a network-reachable unauthenticated integrity bypass with no stated attack complexity. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker with write access to stored OpenPGP AEAD-encrypted files - or positioned as a man-in-the-middle on the encrypted message transport - identifies a ciphertext whose plaintext length is a multiple of the AEAD chunk size, strips one or more trailing data chunks along with the final authentication tag, and patches the outer OpenPGP packet length field to reflect the reduced size. When the intended recipient's Bouncy Castle-based application decrypts the message, each surviving chunk passes its individual tag check, the decrypting stream reaches EOF without verifying the missing final tag, and PGPEncryptedData.verify() returns true - causing the application to silently process truncated plaintext as a fully authentic, unmodified message. …
Remediation The primary fix is to upgrade to a patched release: bc-java 1.85 or later, bc-lts-java 2.73.12 or later, or the appropriate BC-FJA FIPS release - bcpg-fips 1.0.13 for the 1.0.X series, bcpg-fips 2.0.13 for the 2.0.X series, or bcpg-fips 2.1.13 for the 2.1.X series. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, identify all applications and systems using Bouncy Castle for Java by scanning Maven/Gradle build files, classpath configurations, and container images for bc-java, bc-lts-java, or BC-FJA FIPS libraries. …

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Threat intelligence, references, and detailed analysis are available after sign-in.

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
openSUSE Leap 16.0 Fixed
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected

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EUVD-2026-52136 vulnerability details – vuln.today
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