CVE-2026-49095: Improper Input Validation in Kibana Fleet Leading to Privilege Escalation

Synopsis

An improper input validation vulnerability in the Kibana Fleet agent policy management feature allows an authenticated attacker with Fleet management privileges to escalate their own privileges. The vulnerability is reachable over the network and requires no victim interaction, but does require an existing high-privilege Fleet management account. Successful exploitation causes Elastic Agents to be issued API keys with elevated Elasticsearch privileges, granting unauthorized read and write access to sensitive Elasticsearch security indices beyond the intended Fleet role scope. HarborGuard is tracking this advisory and will make a patched-image rebuild available as soon as Elastic publishes a fix version.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the Kibana Fleet API over the network; the service must be exposed to the attacker's network path.

• AuthenticationRequired

  An account holding Fleet management privileges is required; a generic low-privilege account is not sufficient.

• Victim interactionNot required

  No user interaction is needed; the attacker submits malformed policy configuration directly without relying on any other user's actions.

• Attack complexityDetail

  Exploit conditions are straightforward and require no race conditions or special environmental state; a reliable, repeatable request sequence is sufficient.

Blast Radius

• Reads contents of sensitive Elasticsearch security indices, including index data that the Fleet management role is not authorized to access.
• Writes to sensitive Elasticsearch security indices, enabling modification or corruption of security-relevant data such as role mappings or API key records.
• Elastic Agents fleet-wide are issued API keys carrying elevated Elasticsearch privileges, extending the attacker's reach beyond the originating account.