# Exploit Title: AnyDesk allow arbitrary file write by symbolic link attack lead to denial-of-service attack on local machine
\n# Google Dork: [if applicable]\n# Date: 24\/5\/2022
\n# Exploit Author: Erwin Chan
\n# Vendor Homepage: https:\/\/anydesk.com\/en
\n# Software Link: https:\/\/anydesk.com\/en
\n# Version: 7.0.9
\n# Tested on: Windows 11<\/p>\n
It was found that AnyDesk (version 7.0.9) was vulnerable to arbitrary file
\nwrite by symbolic link attack leading to denial-of-service attack on local
\nmachine. It was noted that two functions were affected.<\/p>\n
*Affected function A*
\nWhen there was a remote connection come in, a directory under AppData of
\ncurrent user (without admin privilege) and a “ad.trace” file (i.e.,
\n“C:\\Users\\<user>\\AppData\\Roaming\\AnyDesk”) will be created by “AnyDesk.exe”
\nwith “NT Authority\\SYSTEM” privilege.<\/p>\n
*Affected function B*
\nAfter a connection was made, local or remote user could use the chat room.
\nThe chat log was written to folder
\n“C:\\Users\\<user>\\AppData\\Roaming\\AnyDesk\\chat\\” by “AnyDesk.exe” with “NT
\nAuthority\\SYSTEM” privilege. Or the local user (without admin privilege)
\ncould change the location of the chat log to anywhere that he\/she has
\n“Modify” privilege.<\/p>\n
*Vulnerability Summary*
\nSince the directories (i.e., “C:\\Users\\<user>\\AppData\\Roaming\\AnyDesk\\”,
\n“C:\\Users\\<user>\\AppData\\Roaming\\AnyDesk\\chat\\”) were assigned with
\n“Modify” privilege for current user, current user could modify the entire
\ndirectory. With this setup, an unprivileged user is able to achieve
\narbitrary file write by creating a symbolic link to a privileged location
\n(e.g., C:\\Windows\\System32). As a result, a malicious user could
\npotentially deny any service by overwriting the configuration or system
\nfile of applications such as Anti Virus solutions. It was noted that the
\nfile content could be manipulated in affected function B such that a low
\nprivileged user could write an arbitrary file to an arbitrary location.<\/p>\n
*Affected function A: Exploit steps by local user (without admin privilege)*<\/p>\n
1. Remove the directory “C:\\Users\\<user>\\AppData\\Roaming\\AnyDesk”
\n2. Create symbolic link of “ad.trace” file to a privileged location
\n(e.g., C:\\Windows\\System32\\test.file) (PoC binary could be found here:
\nhttps:\/\/github.com\/googleprojectzero\/symboliclink-testing-tools\/blob\/main\/CreateSymlink\/CreateSymlink_readme.txt
\n)<\/p>\n
1. Connect to local machine (target machine) from a remote machine.
\nAfter the connection was initiated, the content of “ad.trace” file would be
\nwritten to target file (e.g., C:\\Windows\\System32\\test.file)<\/p>\n
*Affected function B: Exploit steps by local user (without admin privilege)*<\/p>\n
1. edit username of remote connector<\/p>\n
1. Establish a AnyDesk connection from remote. Enter arbitrary text into
\nthe chat box. Mark down the filename of chat log<\/p>\n
1. Remove the directory “C:\\Users\\<user>\\AppData\\Roaming\\AnyDesk\\chat”
\n2. Create symbolic link of chat log file (e.g., 657584961.txt) to a
\nprivileged location (e.g., C:\\Windows\\test.conf) (PoC binary could be found
\nhere:
\nhttps:\/\/github.com\/googleprojectzero\/symboliclink-testing-tools\/blob\/main\/CreateSymlink\/CreateSymlink_readme.txt
\n)<\/p>\n
1. Open the chat room and enter arbitrary content into it. After that,
\nthe content of chat room would be written to target file (e.g.,
\nC:\\Windows\\test.conf)<\/p>\n
Please let me know if any detail need further. Thanks<\/p>\n
Regards,
\nErwin<\/p>\n","protected":false},"excerpt":{"rendered":"
# Exploit Title: AnyDesk allow arbitrary file write by symbolic link attack lead to denial-of-service attack on local machine # Google Dork: [if applicable] # Date: 24\/5\/2022 # Exploit Author: Erwin Chan # Vendor Homepage: https:\/\/anydesk.com\/en # Software Link: https:\/\/anydesk.com\/en # Version: 7.0.9 # Tested on: Windows 11 It was found that AnyDesk (version 7.0.9) …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"class_list":["post-26305","post","type-post","status-publish","format-standard","hentry","category-vulnerability"],"_links":{"self":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/26305","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/comments?post=26305"}],"version-history":[{"count":0,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/26305\/revisions"}],"wp:attachment":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/media?parent=26305"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/categories?post=26305"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/tags?post=26305"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}