WinRAR is a trialware file archiver utility for Windows, developed by win.rar GmbH. It can create and view archives in RAR or ZIP file formats, and unpack numerous archive file formats. To enable the user to test the integrity of archives, WinRAR embeds CRC32 or BLAKE2 checksums for each file in each archive. WinRAR supports creating encrypted, multi-part and self-extracting archives. WinRAR is a Windows-only program.
ZIP is an archive file format that supports lossless data compression. A ZIP file may contain one or more files or directories that may have been compressed. The ZIP file format permits a number of compression algorithms, though DEFLATE is the most common. ZIP files generally use the file extensions .zip or .ZIP and the MIME media type application/zip.
RARLabs WinRAR before 6.23 contains a critical security vulnerability. A ZIP archive may include a benign file (such as an ordinary .JPG file) and also a folder that has the same name as the benign file. In vulnerable versions of WinRAR, the contents of the folder (which may include executable content) are processed during an attempt to access only the benign file. This allows threat actors to spoof file extensions, thereby making it possible to launch malicious scripts contained within an archive that masquerades as seemingly innocuous image or text files.
Successful exploit allows attackers to execute arbitrary code when a user attempts to view a benign file within a ZIP archive.
NOTE: This vulnerability has been reported by the CISA (America’s Cyber Defense Agency) to be known to be currently actively exploited in the wild as of August 2023. However security researchers indicate that this vulnerability has been exploited as a zero-day since as early as April 2023. Security researcher “goodbyeselene” reported the vulnerability to RARLAB in early June 2023 and the flaw was publicly disclosed several days after the vendor released an updated version of WinRAR on August 2, 2023.
RARLabs WinRAR before version 6.23.
CRARLabs have released a critical security update in version 6.23, which may be downloaded from the RARLab website at [[https://www.rarlab.com/download.htm]]. Customers are advised to upgrade to the latest version of WinRAR.
NOTE: Remediation of this vulnerability by patching to a specific version indicated may not be sufficient to secure the product against further vulnerabilities discovered in later versions, subsequent to the publication of this guidance. Unless contra-indicated, customers are therefore advised to always upgrade to the latest version of the product available.
(The vendor has not advised of any alternative temporary mitigation or workarounds)
NOTE: Caution should always be taken in applying any temporary mitigations listed. Mitigations are only recommended in cases where patches to remediate the vulnerability are not available, or cannot safely be applied to a given environment immediately. A given mitigation may not in all cases be recommended officially by the application vendor. The viability of any given temporary mitigation measure may vary, depending on server platform and existing configuration. Mitigations listed may incompletely remediate any given vulnerability. Configuration changes to implement listed mitigations may impact/disrupt required functionality within a given customer application. Care should therefore be taken to carefully analyse any listed mitigations for appropriateness to a given environment. Customers are advised to test any configuration changes prior to their being introduced into a production environment.
References * [[https://news.ycombinator.com/item?id=37236100]] * [[https://www.bleepingcomputer.com/news/security/winrar-zero-day-exploited-since-april-to-hack-trading-accounts/]] * [[https://www.group-ib.com/blog/cve-2023-38831-winrar-zero-day/]]
Category: Arbitrary Code Execution
AppCheck has added a plugin to detect the flaw that will run as part of your standard scans.
AppCheck is a software security vendor based in the UK, offering a leading security scanning platform that automates the discovery of security flaws within organisations websites, applications, network, and cloud infrastructure. AppCheck are authorized by the Common Vulnerabilities and Exposures (CVE) Program as a CVE Numbering Authority (CNA).
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