This High severity BASM (Broken Authentication & Session Management) vulnerability known as CVE-2026-12802 was introduced in 4.9.0 and later of Crucible.

This BASM (Broken Authentication & Session Management) vulnerability, with a CVSS Score of 8.7 and a CVSS Vector of 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 allows an unauthenticated attacker to perform actions as another user.

Atlassian recommends that Crucible customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions:

• Crucible 4.9: Upgrade to a release greater than or equal to 4.9.14

See the release notes (https://confluence.atlassian.com/crucible/crucible-releases-298977378.html). You can download the latest version of Crucible from the download center (https://www.atlassian.com/software/crucible/download-archives).

The National Vulnerability Database provides the following description for this vulnerability: In Bouncy Castle for Java before 1.85, CMS AuthEnvelopedData fails to enforce tag-length on decryption. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.12 (1.0.X series), 2.0.12 (2.0.X series) and 2.1.12 (2.1.X series).