CyberSecBulletin
CVE-2026-12817NVD status: Analyzed

BC-JAVA: Improper Validation of Integrity Check Value

Published Updated By the CyberSecBulletin desk

CVE-2026-12817 is a high-severity improper validation of integrity check value vulnerability in BC-JAVA from Legion of the Bouncy Castle, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 1.85 as the first without the flaw, so updating BC-JAVA to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.17% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update BC-JAVA to 1.85 or a later version.
  2. Update BC-LTS-JAVA to 2.73.12 or a later version.
  3. Update BC-FJA to 1.0.13 or 2.0.13 or 2.1.13, whichever matches your release line, or a later version.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Legion of the Bouncy CastleBC-JAVA1.74 up to, but not including, 1.851.85
Legion of the Bouncy CastleBC-LTS-JAVA2.73.0 up to, but not including, 2.73.122.73.12
Legion of the Bouncy CastleBC-FJA1.0.7 up to, but not including, 1.0.13; 2.0.0 up to, but not including, 2.0.13; 2.1.0 up to, but not including, 2.1.131.0.13, 2.0.13, 2.1.13
BouncycastleBcpg-fips1.0.7 up to, but not including, 1.0.13; 2.0.8 up to, but not including, 2.0.13; 2.1.10 up to, but not including, 2.1.131.0.13, 2.0.13, 2.1.13
BouncycastleBouncy Castle For Java LTS2.73.11 and earlierNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
LowSome restricted data can be read.
Integrity
LowLimited modification of data is possible.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.08.7HighCNA
CVSS 3.18.6HighNVD

Official description

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).

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Validation of Integrity Check Value

The product does not validate or incorrectly validates the integrity check values or checksums of a message.

How developers prevent this class of flaw

  • The protocol specification describes the algorithm used for calculating the checksum. It is then a matter of implementing the calculation and verifying that the calculated checksum and the received checksum match.

More Improper Validation of Integrity Check Value vulnerabilities (CWE-354)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in BC-JAVA

All BC-JAVA vulnerabilities

Recent Improper Validation of Integrity Check Value vulnerabilities

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