Vulnerability in Bouncy Castle for Java Affects AuthenticatedData Parsing
CVE-2026-71888

8.7HIGH

Key Information:

Vendor

Legion Of The Bouncy Castle Inc.

Status
Bc-java
Bc-lts-java
Bc-fja
Vendor
CVE Published:
3 October 2026

What is CVE-2026-71888?

In Bouncy Castle for Java before version 1.86, a flaw in the streaming CMS AuthenticatedData parser allows for a message to contain mismatched digestAlgorithm and authAttrs. This flaw can be exploited by an attacker who alters a message in transit, potentially introducing unauthorized authenticated attributes, which may lead to erroneous authorization or routing decisions based on these maliciously modified values. This vulnerability compromises the integrity of message authentication, allowing attackers to manipulate attributes without needing access to the encryption keys. Subsequent versions provide fixes to ensure that mismatches are rejected and improve security against such exploitation.

Affected Version(s)

BC-FJA all 1.0.0 < 1.0.13

BC-FJA all 2.0.0 < 2.0.13

BC-FJA all 2.1.0 < 2.1.13

References

https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2...
vendor-advisory
https://github.com/bcgit/bc-java/commit/dcb683b32b440f1be...
patch

CVSS V4

Score:
8.7
Severity:
HIGH
Confidentiality:
None
Integrity:
High
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Bhargava Shastry
.