CVE-2026-71890 Bouncy Castle - Broken Access Control

Bouncy Castle for Java < 1.86 contains a broken access control vulnerability caused by improper validation of MLS external commit Remove proposals in Group.validateExternalCachedProposals, letting external joiners evict arbitrary group members and take over their slots, exploit requires crafted external commit with Remove proposal.

CVSS base score 8.7 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.25% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Broken Access Control
Impact
Broken Access Control
CVSS vector
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
Published
3 October 2026
Updated
15 October 2026
Weakness
CWE-863

Vendor fix

Update to version 1.86 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

← All CVEs