CVE-2026-71888

Name of the Vulnerable Software and Affected Versions Bouncy Castle for Java versions prior to 1.86 Bouncy Castle for Java LTS versions prior to 2.73.13 Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips versions prior to 1.0.13 Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips versions prior to 2.0.13 Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips versions prior to 2.1.13 Bouncy Castle for Java FIPS (BC-FJA) bcutil-fips versions prior to 2.0.8 Bouncy Castle for Java FIPS (BC-FJA) bcutil-fips versions prior to 2.1.8

Description The streaming CMS AuthenticatedData parser fails to properly validate the consistency between the digestAlgorithm and authAttrs fields. According to RFC 5652, authAttrs must be present whenever digestAlgorithm is. The CMSAuthenticatedDataParser constructor relies solely on digestAlgorithm to determine if authenticated attributes are present. Consequently, if digestAlgorithm is absent but authAttrs is present, the parser verifies the content MAC but returns the attributes via getAuthAttrs() as if they were authenticated, even though the MAC did not cover them. This allows an attacker to modify a message in transit to insert an authenticated attribute, such as an RFC 2634 ESSSecurityLabel, without possessing the key-encryption or content-MAC keys. Applications relying on these attributes for authorization, routing, or labeling decisions may then act on attacker-controlled values.

Recommendations Update Bouncy Castle for Java to version 1.86 or later. Update Bouncy Castle for Java LTS to version 2.73.13 or later. Update Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips to version 1.0.13 or later for the 1.0.X series. Update Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips to version 2.0.13 or later for the 2.0.X series. Update Bouncy Castle for Java FIPS (BC-FJA) bcpkix-fips to version 2.1.13 or later for the 2.1.X series. Update Bouncy Castle for Java FIPS (BC-FJA) bcutil-fips to version 2.0.8 or later for the 2.0.X series. Update Bouncy Castle for Java FIPS (BC-FJA) bcutil-fips to version 2.1.8 or later for the 2.1.X series.