CVE-2026-123204
Description
A flaw was found in Posta. An authenticated remote attacker with editing privileges can exploit a Server-Side Request Forgery (SSRF) vulnerability by configuring webhooks with arbitrary URLs. This issue allows the attacker to force the server to send requests to internal destinations, including private network and cloud metadata addresses. By examining delivery status codes and error messages, the attacker can probe internal services and disclose sensitive network information.
Statement
This vulnerability is rated as Moderate impact because successful exploitation requires an authenticated account with webhook configuration permissions and is constrained to internal network reconnaissance rather than arbitrary code execution. While the flaw permits an authorized user to direct outgoing HTTP requests toward loopback interfaces, private subnets, or cloud metadata endpoints, exposure is restricted to inferring service reachability through response status codes and connection error messages. Furthermore, Posta is not included or shipped in any Red Hat products.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
Frequently Asked Questions
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