Stigmem CVE-2026-76239

Exploitation requires a valid authenticated session on the Stigmem instance, as confirmed by the CVSS 4.0 PR:L metric. The attacker must have permission to create webhook subscriptions - a core product feature available to authenticated users by default. A matching fact-change event must occur (or be triggered by the attacker) to cause delivery to fire. The SSRF is blind: the attacker does not receive the HTTP response from the internal target, limiting direct data exfiltration unless an out-of-band channel exists. Exploitation is further bounded by the network topology: only internal services reachable from the Stigmem server's network interface are exposed. No non-default configuration is required for the vulnerability to exist; the webhook delivery feature is standard. The primary limiting factors are the authentication requirement (PR:L) and the blind nature of the SSRF.

The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N, score 5.3) indicates a network-reachable, low-complexity flaw requiring authenticated access (PR:L) with partial confidentiality, integrity, and availability impact on the vulnerable system and no subsequent-system scope change. The authentication prerequisite is the most meaningful risk-reduction factor relative to raw CVSS: an unauthenticated internet attacker cannot directly exploit this. The blind response behavior further constrains attacker utility for data exfiltration, though POST-based side-effect attacks against unprotected internal services (e.g., Redis without authentication, cloud metadata endpoints) remain viable. No EPSS score was provided, so exploitation probability cannot be numerically benchmarked. No KEV listing and no POC code exist at time of analysis. Deployments where Stigmem is co-located with sensitive, unauthenticated internal APIs or cloud metadata services face the highest realistic risk. The absence of a scope change in the CVSS 4.0 vector suggests the vendor assessed internal service impact as limited or indirect, which is consistent with blind SSRF behavior.

An authenticated Stigmem user creates a webhook subscription specifying delivery_address as http://169.254.169.254/latest/meta-data/ (AWS instance metadata) or http://localhost:6379/ (an unauthenticated Redis instance). When any matching fact-change event is generated within Stigmem, the server automatically issues a blind HTTP POST to that internal address. The attacker infers service reachability and possible state changes through secondary effects, such as data written to Redis or metadata service access logs, without receiving the response body directly.