Info-ZIP UnZip zipinfo.c Denial of Service Vulnerability [CVE-2016-9844]

CVE Number – CVE-2016-9844

A vulnerability in the zi_short function of Info-Zip UnZip could allow a local attacker to cause a denial of service (DoS) condition on a targeted system.
The vulnerability is due to a buffer overflow condition that could occur in the zi_short function, as defined in the zipinfo.c source code file of the affected software, when processing a large compression method value in the central directory file header. An attacker could exploit this vulnerability by decompressing a ZIP archive that submits malicious input to the targeted system. A successful exploit could result in a DoS condition. 

Proof-of-concept (PoC) code that demonstrates an exploit of this vulnerability is publicly available. 

Info-ZIP has not confirmed the vulnerability and software updates are not available.


  • To exploit this vulnerability, the attacker must have user-level access to the targeted system. This access requirement could reduce the likelihood of a successful exploit.At the time this alert was first published, a source code update patch has been made available; however, the patch has not been committed into the upstream source code repository.


  • Administrators are advised to contact the vendor regarding future updates and releases.

    Administrators are advised to allow only trusted users to have network access.

    Administrators are advised to use an unprivileged account when browsing the Internet.

    Administrators are advised to monitor critical systems.

    Users are advised not to open email messages from suspicious or unrecognized sources. If users cannot verify that links or attachments included in email messages are safe, they are advised not to open them.

    Users are advised not to visit websites or follow links that have suspicious characteristics or cannot be verified as safe.

Vendor Announcements

  • At the time this alert was first published, Info-ZIP had not released a security announcement.

Fixed Software

  • At the time this alert was first published, Info-ZIP had not released software updates.

Duncan Newell

Duncan is a technology professional with over 20 years experience of working in various IT roles. He has a interest in cyber security, and has a wide range of other skills in radio, electronics and telecommunications.

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