1 Vulnerability Overview
Recently, a security researcher found a logical bug in WinRAR using the WinAFL fuzzer and exploited it to gain full control over a victim’s computer. An attacker could exploit this vulnerability by crafting an archive and then tricking victims into downloading it by means of a phishing email, net disk, or forum. When a victim opens this malicious file with WinRAR, the attack is complete.
The vulnerability exists in UNACEV2.dll in WinRAR, which does not properly sanitize file names when decompressing .ace files, leading to directory traversal. This indicates that an attacker could write a malicious file to an arbitrary path, thus making it possible to plant a backdoor trojan. This vulnerability has been in WinRAR for more than 19 years. Now WinRAR has to completely stop supporting the vulnerable format (.ace).
WinRAR is a Windows data compression/decompression tool that can be used to create and view RAR or ZIP compression files and decompress files of various compression formats. As the most popular compression tool, WinRAR has more than 500 million users around the world.
2 Scope of Impact
- Affected versions:
WinRAR < 5.70 Beta 1
- Unaffected versions:
WinRAR 5.70 Beta 1
Our inspection finds that some other compression tools also incorporate UNACEV2.dll and are therefore possibly affected by this vulnerability. Users of these tools should also check for official upgrade notices or delete UNACEV2.dll. Following is an incomplete list of compression tools incorporating UNACEV2.dll.
|Bandizip||< = 126.96.36.199|
|Haozip (2345)||< = 188.8.131.5207|
|360Zip||< = 184.108.40.2060|
3 Recommended Solution
3.1 Version Upgrade
WinRAR 5.70 Beta 1 deletes UNACEV2.dll so as not to decompress .ace files. Therefore, users can upgrade WinRAR to this version to protect against this vulnerability.
- 32-bit: http://win-rar.com/fileadmin/winrar-versions/wrar57b1.exe
- 64-bit: http://win-rar.com/fileadmin/winrar-versions/winrar-x64-57b1.exe
3.2 Deletion of the Vulnerable File
Users who cannot upgrade to the latest version for the time being can protect against this vulnerability by deleting UNACEV2.DLL from the WinRAR installation directory.
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