Krill encrypts each login‑session token with a nonce derived from a counter that is reset to zero on every server restart. Because the same cryptographic key and nonce pair are reused after each restart, an authenticated user can generate a valid “admin” session token by simply recreating the token’s cryptographic parameters. The result is a privilege escalation that allows a non‑admin user to gain full administrative control of the Krill service.

The vulnerability affects Krill by NLnet Labs. All versions released prior to 0.16.1 are impacted. Versions 0.16.1 and later include the patch that generates a new nonce on each encryption instance, preventing reuse.

The CVSS score of 8.4 classifies this flaw as high severity, indicating significant impact if exploited. The EPSS score is currently not available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog, suggesting that documented exploitation is not yet observed. The likely attack vector is that a user who can log in to Krill can forge an admin token; this would occur after any server restart when the nonce counter is reset, making the forgery possible on any authenticated session over the network.