7.8 CVE-2025-21204

Path Traversal

Improper link resolution before file access ('link following') in Windows Update Stack allows an authorized attacker to elevate privileges locally.
https://nvd.nist.gov/vuln/detail/CVE-2025-21204

Categories

CWE-59 : Improper Link Resolution Before File Access ('Link Following')
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource. Some people use the phrase "insecure temporary file" when referring to a link following weakness, but other weaknesses can produce insecure temporary files without any symlink involvement at all. "Zip slip" is an attack that uses file archives (e.g., ZIP, tar, rar, etc.) that contain filenames with path traversal sequences that cause the files to be written outside of the directory under which the archive is expected to be extracted [REF-1282]. It is most commonly used for relative path traversal (CWE-23) and link following (CWE-59). Some versions of Perl follow symbolic links when running with the -e option, which allows local users to overwrite arbitrary files via a symlink attack. Text editor follows symbolic links when creating a rescue copy during an abnormal exit, which allows local users to overwrite the files of other users. Antivirus update allows local users to create or append to arbitrary files via a symlink attack on a logfile. Symlink attack allows local users to overwrite files. Window manager does not properly handle when certain symbolic links point to "stale" locations, which could allow local users to create or truncate arbitrary files. Second-order symlink vulnerabilities Second-order symlink vulnerabilities Symlink in Python program Setuid product allows file reading by replacing a file being edited with a symlink to the targeted file, leaking the result in error messages when parsing fails. Signal causes a dump that follows symlinks. Hard link attack, file overwrite; interesting because program checks against soft links Hard link and possibly symbolic link following vulnerabilities in embedded operating system allow local users to overwrite arbitrary files. Server creates hard links and unlinks files as root, which allows local users to gain privileges by deleting and overwriting arbitrary files. Operating system allows local users to conduct a denial of service by creating a hard link from a device special file to a file on an NFS file system. Web hosting manager follows hard links, which allows local users to read or modify arbitrary files. Package listing system allows local users to overwrite arbitrary files via a hard link attack on the lockfiles. Hard link race condition Mail client allows remote attackers to bypass the user warning for executable attachments such as .exe, .com, and .bat by using a .lnk file that refers to the attachment, aka "Stealth Attachment." FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file. FTP server allows remote attackers to read arbitrary files and directories by uploading a .lnk (link) file that points to the target file. Browser allows remote malicious web sites to overwrite arbitrary files by tricking the user into downloading a .LNK (link) file twice, which overwrites the file that was referenced in the first .LNK file. ".LNK." - .LNK with trailing dot Rootkits can bypass file access restrictions to Windows kernel directories using NtCreateSymbolicLinkObject function to create symbolic link File system allows local attackers to hide file usage activities via a hard link to the target file, which causes the link to be recorded in the audit trail instead of the target file. Web server plugin allows local users to overwrite arbitrary files via a symlink attack on predictable temporary filenames. A Libcontainer used in Docker Engine allows local users to escape containerization and write to an arbitrary file on the host system via a symlink attack in an image when respawning a container. "Zip Slip" vulnerability in Go-based Open Container Initiative (OCI) registries product allows writing arbitrary files outside intended directory via symbolic links or hard links in a gzipped tarball. "Zip Slip" vulnerability in container management product allows writing arbitrary files outside intended directory via a container image (.tar format) with filenames that are symbolic links that point to other files within the same tar file; however, the files being pointed to can also be symbolic links to destinations outside the intended directory, bypassing the initial check.

References

af854a3a-2127-422b-91ae-364da2661108

https://www.vicarius.io/vsociety/posts/cve-2025-21204-privilege-elevation-vul... Tool Signature
https://www.vicarius.io/vsociety/posts/cve-2025-21204-privilege-elevation-vul... Mitigation

secure@microsoft.com

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21204 Vendor Advisory

CPE

cpe	start	end
Configuration 1
cpe:2.3:o:microsoft:windows_10_1507:::::::x64:*		< 10.0.10240.20978
cpe:2.3:o:microsoft:windows_10_1507:::::::x86:*		< 10.0.10240.20978
cpe:2.3:o:microsoft:windows_10_1607:::::::x64:*		< 10.0.14393.7969
cpe:2.3:o:microsoft:windows_10_1607:::::::x86:*		< 10.0.14393.7969
cpe:2.3:o:microsoft:windows_10_1809:::::::x64:*		< 10.0.17763.7136
cpe:2.3:o:microsoft:windows_10_1809:::::::x86:*		< 10.0.17763.7136
cpe:2.3:o:microsoft:windows_10_21h2::::::::		< 10.0.19044.5737
cpe:2.3:o:microsoft:windows_10_22h2::::::::		< 10.0.19045.5737
cpe:2.3:o:microsoft:windows_11_22h2::::::::		< 10.0.22621.5189
cpe:2.3:o:microsoft:windows_11_23h2::::::::		< 10.0.22631.5189
cpe:2.3:o:microsoft:windows_11_24h2::::::::		< 10.0.26100.3775
cpe:2.3:o:microsoft:windows_server_2008:-:sp2:::::x64:*
cpe:2.3:o:microsoft:windows_server_2008:-:sp2:::::x86:*
cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:::::x64:*
cpe:2.3:o:microsoft:windows_server_2012:-:::::::*
cpe:2.3:o:microsoft:windows_server_2012:r2:::::::*
cpe:2.3:o:microsoft:windows_server_2016::::::::		< 10.0.14393.7969
cpe:2.3:o:microsoft:windows_server_2019::::::::		< 10.0.17763.7136
cpe:2.3:o:microsoft:windows_server_2022::::::::		< 10.0.20348.3453
cpe:2.3:o:microsoft:windows_server_2022_23h2::::::::		< 10.0.25398.1551
cpe:2.3:o:microsoft:windows_server_2025::::::::		< 10.0.26100.3775

REMEDIATION

EXPLOITS

Exploit-db.com

id	description	date
No known exploits

POC Github

Url
No known exploits

Other Nist (github, ...)

Url
No known exploits

CAPEC

Common Attack Pattern Enumerations and Classifications

id	description	severity
132	Symlink Attack An adversary positions a symbolic link in such a manner that the targeted user or application accesses the link's endpoint, assuming that it is accessing a file with the link's name. [Identify Target] Adversary identifies the target application by determining whether there is sufficient check before writing data to a file and creating symlinks to files in different directories. [Try to create symlinks to different files] The adversary then uses a variety of techniques, such as monitoring or guessing to create symlinks to the files accessed by the target application in the directories which are identified in the explore phase. [Target application operates on created symlinks to sensitive files] The adversary is able to create symlinks to sensitive files while the target application is operating on the file.	High
17	Using Malicious Files An attack of this type exploits a system's configuration that allows an adversary to either directly access an executable file, for example through shell access; or in a possible worst case allows an adversary to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface. [Determine File/Directory Configuration] The adversary looks for misconfigured files or directories on a system that might give executable access to an overly broad group of users. [Upload Malicious Files] If the adversary discovers a directory that has executable permissions, they will attempt to upload a malicious file to execute. [Execute Malicious File] The adversary either executes the uploaded malicious file, or executes an existing file that has been misconfigured to allow executable access to the adversary.	Very High
35	Leverage Executable Code in Non-Executable Files An attack of this type exploits a system's trust in configuration and resource files. When the executable loads the resource (such as an image file or configuration file) the attacker has modified the file to either execute malicious code directly or manipulate the target process (e.g. application server) to execute based on the malicious configuration parameters. Since systems are increasingly interrelated mashing up resources from local and remote sources the possibility of this attack occurring is high.	Very High
76	Manipulating Web Input to File System Calls An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible. [Fingerprinting of the operating system] In order to create a valid file injection, the attacker needs to know what the underlying OS is so that the proper file seperator is used. [Survey the Application to Identify User-controllable Inputs] The attacker surveys the target application to identify all user-controllable inputs, possibly as a valid and authenticated user [Vary inputs, looking for malicious results] Depending on whether the application being exploited is a remote or local one, the attacker crafts the appropriate malicious input containing the path of the targeted file or other file system control syntax to be passed to the application [Manipulate files accessible by the application] The attacker may steal information or directly manipulate files (delete, copy, flush, etc.)	Very High

MITRE

Techniques

id	description
T1027.006	Obfuscated Files or Information: HTML Smuggling
T1027.009	Obfuscated Files or Information: Embedded Payloads
T1547.009	Boot or Logon Autostart Execution:Shortcut Modification
T1564.009	Hide Artifacts: Resource Forking
T1574.005	Hijack Execution Flow: Executable Installer File Permissions Weakness
T1574.010	Hijack Execution Flow: ServicesFile Permissions Weakness
© 2022 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation.

Mitigations

id	description
M1048	Browser sandboxes can be used to mitigate some of the impact of exploitation, but sandbox escapes may still exist.
M1040	On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent execution of potentially obfuscated scripts.
M1018	Limit Privileges for Shortcut Creation: While the SeCreateSymbolicLinkPrivilege is not directly related to .lnk file creation, you should still enforce least privilege principles by limiting user rights to create and modify shortcuts, especially in system-critical locations. This can be done through GPO: Computer Configuration > [Policies] > Windows Settings > Security Settings > Local Policies > User Rights Assignment: Create symbolic links. Regular User Permissions Review: Regularly review and audit user permissions to ensure that only necessary accounts have write access to startup folders and critical system directories.
M1013	Configure applications to use the application bundle structure which leverages the <code>/Resources</code> folder location.
M1018	Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service binary target path locations. Deny execution from user directories such as file download directories and temp directories where able.
M1018	Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service binary target path locations. Deny execution from user directories such as file download directories and temp directories where able.
© 2022 The MITRE Corporation. Esta obra se reproduce y distribuye con el permiso de The MITRE Corporation.

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cpe	start	end
Configuration 1
cpe:2.3:o:microsoft:windows_10_1507:::::::x64:*		< 10.0.10240.20978
cpe:2.3:o:microsoft:windows_10_1507:::::::x86:*		< 10.0.10240.20978
cpe:2.3:o:microsoft:windows_10_1607:::::::x64:*		< 10.0.14393.7969
cpe:2.3:o:microsoft:windows_10_1607:::::::x86:*		< 10.0.14393.7969
cpe:2.3:o:microsoft:windows_10_1809:::::::x64:*		< 10.0.17763.7136
cpe:2.3:o:microsoft:windows_10_1809:::::::x86:*		< 10.0.17763.7136
cpe:2.3:o:microsoft:windows_10_21h2::::::::		< 10.0.19044.5737
cpe:2.3:o:microsoft:windows_10_22h2::::::::		< 10.0.19045.5737
cpe:2.3:o:microsoft:windows_11_22h2::::::::		< 10.0.22621.5189
cpe:2.3:o:microsoft:windows_11_23h2::::::::		< 10.0.22631.5189
cpe:2.3:o:microsoft:windows_11_24h2::::::::		< 10.0.26100.3775
cpe:2.3:o:microsoft:windows_server_2008:-:sp2:::::x64:*
cpe:2.3:o:microsoft:windows_server_2008:-:sp2:::::x86:*
cpe:2.3:o:microsoft:windows_server_2008:r2:sp1:::::x64:*
cpe:2.3:o:microsoft:windows_server_2012:-:::::::*
cpe:2.3:o:microsoft:windows_server_2012:r2:::::::*
cpe:2.3:o:microsoft:windows_server_2016::::::::		< 10.0.14393.7969
cpe:2.3:o:microsoft:windows_server_2019::::::::		< 10.0.17763.7136
cpe:2.3:o:microsoft:windows_server_2022::::::::		< 10.0.20348.3453
cpe:2.3:o:microsoft:windows_server_2022_23h2::::::::		< 10.0.25398.1551
cpe:2.3:o:microsoft:windows_server_2025::::::::		< 10.0.26100.3775