NLnet Labs Krill EUVD-2026-115257

Requires a multi-tenant/shared Krill deployment where the target CA's parent CA is hosted on the same Krill server as the attacker's CA - the in-process shortcut that skips signed-CMS verification only triggers when parent and child are co-located. The attacker must be an authenticated Krill operator (PR:L) able to configure a CA's parent contact and supply an arbitrary child_handle. Limiting factors: single-server/single-tenant deployments where parents are not co-located are not reachable by this path; the attacker needs valid authenticated access to the Krill instance; and the supplied vector rates attack complexity as high, though the sources do not describe what makes the trigger difficult.

The input signals point to a credible but conditional authorization-bypass issue (CWE-639) rather than a mass-exploitation emergency. The provided CVSS 3.1 vector (AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L, base 8.4) describes a network-reachable flaw requiring low privileges (PR:L = an authenticated Krill user/CA operator), no user interaction, raised attack complexity, and a scope change - consistent with one authenticated tenant crossing into another tenant's authorization domain. The vuln.today Decision label is 'this_week' (not act_now/emergency), which fits the picture of a serious multi-tenant trust flaw that is not yet known to be weaponized. There is no KEV listing and no EPSS score in the input, so widespread or automated exploitation is not evidenced; this is best read as a latent privilege/authorization defect requiring specific conditions, not a widely-fired exploit. No public exploit was identified - the single reference is a vendor advisory, not PoC code. Key missing data: the input provides no EPSS probability, no KEV status, and no fixed-version information, so remediation timing cannot be stated from this data. Note also that AC:H is asserted in the supplied vector but the available sources do not describe the trigger mechanism beyond the co-located-parent condition, so the complexity rating cannot be independently explained from evidence.

On a Krill server hosting multiple certificate authorities where a target CA's parent lives on the same server, an authenticated operator configures their own CA's parent contact and sets the child_handle to another CA's identity. Because the in-process RFC 6492 provisioning exchange trusts the caller-supplied child_handle without verifying it belongs to the requesting CA, the attacker can act as that other child and manipulate its provisioning. No public exploit code was identified; exploitation requires authenticated access to the shared Krill instance.