CVE-2026-24117 is a medium severity SSRF vulnerability in the sigstore rekor software supply chain transparency log, specifically in versions 1.4.3 and earlier. The vulnerability exists in the /api/v1/index/retrieve endpoint, which accepts a user-provided URL to retrieve a public key. This design flaw allows an attacker to induce the server to perform HTTP GET requests to arbitrary internal or external URLs. Because the SSRF only supports GET requests, it cannot alter the state of targeted services, and the server does not relay the response back to the attacker, preventing direct data exfiltration. However, attackers can perform blind SSRF attacks to map internal network topology or identify accessible internal services, which could be leveraged in multi-stage attacks. The vulnerability is classified under CWE-918 (Server-Side Request Forgery). The issue was publicly disclosed on January 22, 2026, and fixed in rekor version 1.5.0. Until patching, disabling the vulnerable retrieve API endpoint using the --enable_retrieve_api=false flag serves as an effective mitigation. No known exploits are currently reported in the wild.

For European organizations using sigstore rekor versions prior to 1.5.0, this SSRF vulnerability poses a risk of internal network reconnaissance by unauthorized actors. Although the vulnerability does not allow direct data theft or service disruption, it can facilitate lateral movement or identification of sensitive internal services, increasing the attack surface for subsequent exploitation. Organizations relying on rekor for software supply chain transparency may face risks to the confidentiality of their internal infrastructure layout. This is particularly relevant for critical infrastructure providers, government agencies, and large enterprises in Europe that adopt sigstore for software integrity verification. The inability to exfiltrate data limits immediate damage, but the reconnaissance capability could aid sophisticated attackers in planning further attacks, especially in environments with weak internal segmentation or insufficient monitoring of internal traffic.

European organizations should promptly upgrade sigstore rekor to version 1.5.0 or later to remediate this vulnerability. If immediate patching is not feasible, disabling the vulnerable /api/v1/index/retrieve endpoint by setting --enable_retrieve_api=false is strongly recommended to prevent SSRF exploitation. Network-level controls should be implemented to restrict outbound HTTP requests from rekor servers to only trusted destinations, minimizing the risk of SSRF abuse. Additionally, internal network segmentation and monitoring should be enhanced to detect anomalous internal requests originating from the rekor server. Security teams should audit usage logs for unusual access patterns to the retrieve API endpoint and conduct penetration testing to identify potential SSRF exploitation paths. Finally, organizations should incorporate this vulnerability into their risk management and incident response plans, ensuring readiness for potential SSRF-related reconnaissance activities.