CVE-2026-26215 is a critical vulnerability in the manga-image-translator software, specifically versions beta-0.3 and earlier, which operate in shared API mode. The core issue is unsafe deserialization of untrusted data via Python's pickle.loads() function within two FastAPI endpoints: /simple_execute/{method} and /execute/{method}. These endpoints accept request bodies that are deserialized without any validation or sanitization, allowing attackers to craft malicious pickle payloads that execute arbitrary code on the server. Although the software attempts to enforce a nonce-based authorization check to restrict access, this mechanism is flawed because the nonce defaults to an empty string and the check is effectively bypassed. Consequently, remote attackers can exploit this vulnerability without authentication or user interaction. The vulnerability is classified under CWE-502 (Deserialization of Untrusted Data), which is a well-known vector for remote code execution attacks. The CVSS 4.0 score of 9.3 reflects the critical nature of this flaw, highlighting its network attack vector, low attack complexity, no privileges or user interaction required, and high impact on confidentiality, integrity, and availability. No patches or mitigations have been officially released at the time of publication, and no known exploits have been observed in the wild. However, the vulnerability poses a significant risk to any deployment of manga-image-translator in shared API mode, especially in environments exposed to untrusted networks. Attackers exploiting this flaw could gain full control over affected servers, leading to data breaches, service disruption, or further lateral movement within networks.

For European organizations, this vulnerability presents a severe risk due to the potential for unauthenticated remote code execution on servers running manga-image-translator. Organizations involved in digital media, content translation, or manga-related services that utilize this software could face data breaches, service outages, or complete system compromise. The ability to execute arbitrary code remotely without authentication means attackers can deploy malware, exfiltrate sensitive information, or pivot to other internal systems. Given the critical CVSS score and the nature of the flaw, the impact on confidentiality, integrity, and availability is high. Additionally, organizations subject to strict data protection regulations such as GDPR could face legal and financial repercussions if exploited. The lack of a patch increases the urgency for immediate mitigation. The threat is amplified in shared API mode deployments exposed to the internet or untrusted networks, common in cloud or hybrid environments. This vulnerability could also be leveraged in targeted attacks against European media companies or research institutions working with manga or image translation technologies.

1. Immediately disable or restrict access to the vulnerable FastAPI endpoints (/simple_execute/{method} and /execute/{method}) until a secure patch or update is available. 2. Avoid using pickle.loads() or any unsafe deserialization methods on untrusted input; replace with safer serialization formats such as JSON or implement strict input validation and allowlisting. 3. Implement strong authentication and authorization controls around API endpoints, ensuring nonce or token mechanisms are correctly configured and enforced. 4. Conduct thorough code reviews and security audits of any deserialization logic to identify and remediate unsafe practices. 5. Employ network-level protections such as firewalls or API gateways to limit exposure of these endpoints to trusted networks only. 6. Monitor logs and network traffic for suspicious activity indicative of exploitation attempts, such as unusual payloads or unexpected API calls. 7. Prepare incident response plans to quickly isolate and remediate affected systems if exploitation is detected. 8. Engage with the vendor or community to track the release of official patches or updates and apply them promptly once available.