libcurl might in some circumstances reuse the wrong connection when asked to do Negotiate-authenticated ones, even when they are set to use different 'services'.
libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead.
When reusing a connection a range of criteria must be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different services.
Exploitability
AV:NAC:LPR:LUI:NScope
S:UImpact
C:NI:HA:N6.5/CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N