Overview
CVE-2025-66548 describes a low-severity vulnerability affecting Nextcloud Deck, a kanban-style organization tool integrated within Nextcloud. This vulnerability allows an attacker to spoof the file extension of downloaded files by utilizing Right-to-Left Override (RTLO) characters. This can trick users into downloading and potentially executing files with a different extension than what is displayed, potentially leading to unintended consequences.
Technical Details
The vulnerability resides in how Nextcloud Deck handles file names during download. By injecting RTLO characters into the file name, the displayed extension can be manipulated. For instance, a file named “evil_exe.txt” (where “” represents the RTLO character) would be displayed as “evil_txt.exe” in some contexts, potentially misleading a user into executing a malicious executable disguised as a harmless text file.
This issue has been addressed by properly sanitizing file names and preventing the use of RTLO characters in the affected versions.
CVSS Analysis
- Severity: LOW
- CVSS Score: 3.3
The low severity reflects the relatively limited impact and the requirement of user interaction to trigger the vulnerability. The attacker must convince the user to download and execute the manipulated file. The CVSS score reflects the potential for limited impact, but due to the user interaction needed is not considered a higher risk.
Possible Impact
While the severity is low, the potential impact of this vulnerability includes:
- Malware Execution: Users may inadvertently download and execute malicious files believing them to be safe based on the spoofed extension.
- Social Engineering: This vulnerability can be used as part of a social engineering attack to trick users into performing actions they wouldn’t normally do.
Mitigation or Patch Steps
To mitigate this vulnerability, it is highly recommended to upgrade Nextcloud Deck to one of the following versions or later:
- 1.12.7
- 1.14.4
- 1.15.1
Regularly updating your Nextcloud Deck installation is crucial for maintaining a secure environment.
