CVE-2026-94588 in pmg-api
Summary
by MITRE • 09/22/2026
In Proxmox pmg-api, an argument injection vulnerability exists in the package changelog retrieval functionality. This is caused by improper handling of user-supplied input passed to the underlying apt-get command when fetching package changelogs. It requires authentication but can be exploited in a CSRF-style attack.
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Analysis
by VulDB Data Team • 09/22/2026
The Proxmox Mail Gateway pmg-api component contains an argument injection vulnerability within its package changelog retrieval functionality, representing a significant security flaw that compromises the integrity of system administration interfaces. This vulnerability stems from improper input validation and sanitization mechanisms when processing user-supplied data intended for fetching software package change logs. The core technical issue lies in how the application constructs commands to interact with the underlying apt-get utility, failing to adequately restrict or escape special characters that could alter command execution flow.
From a technical perspective, this flaw is classified under CWE-78 Improper Neutralization of Special Elements used in an OS Command, commonly known as OS Command Injection. The vulnerability arises because the application passes unsanitized user input directly into shell commands without sufficient filtering for metacharacters such as semicolons, ampersands, or pipe symbols. When a request is made to retrieve changelogs, the system constructs an apt-get command string that incorporates the provided parameters. If these parameters contain maliciously crafted sequences, they can break out of the intended argument context and inject additional commands into the shell execution environment.
Although exploitation requires authentication, which limits immediate exposure to unauthenticated attackers, the requirement for valid credentials does not eliminate risk due to the potential for Cross-Site Request Forgery attacks. An attacker who has obtained or guessed administrative credentials could leverage CSRF techniques to trick an authenticated administrator's browser into sending a malicious request to the pmg-api endpoint. Because many web applications do not adequately verify the origin of requests or implement robust anti-CSRF tokens, this vector allows remote code execution without direct user interaction beyond clicking a link or loading a page crafted by the attacker.
The operational impact of successfully exploiting this vulnerability is severe, as it grants an attacker arbitrary command execution capabilities on the host system running Proxmox Mail Gateway. Depending on the privileges under which the pmg-api service operates, typically root or high-privilege user contexts, the attacker could install malicious packages, exfiltrate sensitive data, modify configuration files, or establish persistent backdoors within the mail gateway infrastructure. This compromises not only the confidentiality and integrity of the email security appliance but also potentially affects downstream systems connected to it through compromised network traffic analysis or interception capabilities enabled by the breached gateway.
Mitigation strategies should focus on both immediate remediation and long-term architectural improvements. The primary defense is applying vendor-provided patches that address this specific argument injection flaw in the pmg-api package, ensuring that input validation strictly limits allowed characters for changelog retrieval parameters. Additionally, implementing strict Content Security Policy headers and robust anti-CSRF token mechanisms can prevent unauthorized state-changing requests even if credentials are compromised. Network segmentation should also be reviewed to ensure that management interfaces like pmg-api are not exposed directly to untrusted networks, reducing the attack surface available to potential adversaries seeking to exploit this vulnerability through web-based vectors.