Description

Privilege escalation in the DLL Services component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-29T13:17:45.180Z",
  "pubdate": "2026-09-29T13:17:45.180Z",
  "executiveSummary": "A local privilege escalation vulnerability exists within the DLL Services component of Firefox. This flaw allows an attacker with low-privilege access to the host system to execute arbitrary code with elevated permissions, bypassing standard security boundaries.\nThe vulnerability resides in the way the DLL Services component manages or loads libraries, potentially leading to unauthorized system-level operations. Successful exploitation enables an attacker to transition from a restricted user context to a higher-privileged state, significantly increasing the impact of a system compromise.\nThe affected versions include Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17. The risk implication is severe, as privilege escalation often serves as a critical component in advanced persistent threat (APT) chains, allowing attackers to gain persistence, disable security software, or exfiltrate sensitive data. Exploitation generally requires the attacker to have already achieved initial foothold on the local machine.\nSecurity teams must prioritize patching these versions to eliminate the vulnerability. The attack does not necessarily require network exposure, as it is a local exploitation vector targeting the interaction between the application's service architecture and the underlying operating system's privilege management mechanisms.",
  "technicalDetails": "The vulnerability is localized within the DLL Services component, which is responsible for managing dynamic link library operations for the browser. The root cause pertains to improper validation or unsafe handling of library loading procedures, which can be leveraged to achieve unauthorized execution of malicious payloads.\nExploitation typically involves an attacker manipulating the environment or the file system to influence the DLL loading sequence. If the DLL Services component fails to strictly verify the integrity, origin, or path of a requested library, an attacker can substitute a malicious DLL (DLL hijacking) or exploit a race condition during the loading process.\nThe attack flow follows these logical steps: First, the attacker identifies the directory or path where the DLL Services component attempts to load a library. Second, the attacker places a maliciously crafted library within the target search path or alters symbolic links to redirect the loading mechanism to the attacker-controlled library. Third, when the DLL Services component triggers a service operation or initialization sequence, it inadvertently executes the code within the malicious library. Because the DLL Services component operates with elevated system or administrative privileges, the injected code inherits these permissions.\nThis execution leads to a classic privilege escalation scenario. By achieving execution at this level, an attacker can bypass Access Control Lists (ACLs), interact with kernel-level functions, and circumvent OS-level protections like User Account Control (UAC). The vulnerability is particularly dangerous because it exploits the trusted nature of the browser's background services, which often run in the background without user interaction or visual feedback.\nThe scope of impact is widespread across the affected versions: Firefox ESR 153.4, Firefox 157, and Firefox ESR 140.17. While the vulnerability requires the attacker to have existing, limited local access, it removes the need for additional OS-level vulnerabilities to gain full system control. The payload behavior following successful exploitation typically involves the deployment of secondary malware, the creation of hidden administrative accounts, or the modification of sensitive system registry keys to ensure long-term persistence in the system environment."
}