[UNIX] Multiple Vulnerabilities in Monit

From: SecuriTeam (support_at_securiteam.com)
Date: 04/11/04

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      Multiple Vulnerabilities in Monit
    ------------------------------------------------------------------------

    SUMMARY

     <http://www.tildeslash.com/monit/> Monit is "a utility for managing and
    monitoring, processes, files, directories and devices on a UNIX system.
    Monit conducts automatic maintenance and repair and can execute meaningful
    causal actions in error situations". Several vulnerabilities allow a
    remote attacker with access to Monit's WBA via HTTP or HTTPS clients to
    potentially gain the privileges of the root user.

    DETAILS

    Vulnerable Systems:
     * Stable: Monit 4.2 and prior
     * Beta: Monit 4.3 Beta 2 and prior

    Immune Systems:
     * Stable: Monit 4.2.1
     * Beta: Monit 4.3 Beta 3

    Three vulnerabilities were found in Monit during a simple code review. All
    of the vulnerabilities are in Monit's HTTP/HTTPS administration
    interfaces, and as such can only be exploited if the interface is enabled
    and accessible. Two of the vulnerabilities lie in the Basic authentication
    code, while one vulnerability lies in the processing of POST requests.

     * Basic Authentication Out-of-Bounds Read (Denial of Service)
    When faced with a Basic authentication request without a password, Monit
    will decrement a pointer returned by a strchr() call without appropriate
    NULL pointer checking. The error results in a segmentation fault during a
    strcpy() call. This request can be generated with a simple web browser.
    This vulnerability does not allow users to gain privileges on the server.
    For instance. Specifically, if the base64-decoded credentials string does
    not contain a colon, the vulnerability can be exploited.

     * Basic Authentication Buffer Overflow (Remote Root)
    When faced with a Basic authentication request with an overly long user
    name (> 256 characters), vulnerable versions of Monit will overrun a
    stack-based buffer. This potentially allows a remote attacker to gain root
    privileges.

     * POST Input Off-By-One (Exploitability Varies)
    When faced with a POST submission that is exactly 1,024 bytes, Monit
    suffers from an off-by-one overflow. The ability to exploit this
    vulnerability depends on the version of gcc used to compile the
    application. Some compilers will allow this overflow to modify the frame
    pointer, potentially controlling stack frames.

     * Integer Overflow in POST Input Handler (UPDATE to the vulnerability
    discovered by S-Quadra)
    S-Quadra discovered that a large HTTP POST would cause an xmalloc() call
    within the WBA to fail. This issue was fixed in 4.2.1 as a denial of
    service. In fact, this code also contained an exploitable integer
    overflow. By specifying a Content-Length header of -1, a zero-byte heap
    allocation is performed. An attacker can then input an arbitrary amount of
    data, overwriting significant portions of the heap. Matthew Murphy's
    research suggests that this issue could also be exploited.

    Vendor Status:
    April 3, 2004:
     * First two vulnerabilities discovered
     * Monit team notified via e-mail (monitgroup@tildeslash.com)
    April 4, 2004:
     * Response from Jan Henrik-Haukeland (hauk@tildeslash.com)
     * Patch for first two reports committed to CVS
     * Third vulnerability discovered
     * Monit team notified via e-mail (monitgroup@tildeslash.com)
    April 5, 2004:
     * Response from Jan Henrik-Haukeland (hauk@tildeslash.com)
     * Patch for third issue committed to CVS
     * Monit team releases security advisory
     * Monit 4.2.1 released
     * Monit 4.3 Beta 3 released
     * Public disclosure

    The Monit team deserves praise on a very speedy response to this
    vulnerability. Particularly noteworthy is that the vendor was notified
    shortly before midnight on April 4, 2004. The patch for each of these
    issues was committed to CVS within 18 hours of the initial report. Thanks
    to Jan Henrik-Haukeland for a fast response to this issue.

    Workaround
    For those who cannot immediately upgrade packages, it is recommended that
    the Monit HTTP interface be disabled. If access to this interface is
    necessary, limit it to the Local Area Network with appropriate firewall
    rules. Upgrading as listed below is recommended if possible. For those
    users of Monit who have deployed vendor-provided packages, it is
    recommended to wait for updated vendor binaries.

    Solution
    * Monit 4.2 Stable: The vendor has released Monit 4.2.1, which contains
    these fixes. It can be downloaded at:
     <http://www.tildeslash.com/monit/dist/monit-4.2.1.tar.gz>
    http://www.tildeslash.com/monit/dist/monit-4.2.1.tar.gz
    MD5 Checksum:
    <http://www.tildeslash.com/monit/dist/monit-4.2.1.tar.gz.md5>
    http://www.tildeslash.com/monit/dist/monit-4.2.1.tar.gz.md5

    * Monit 4.3 Beta: The vendor has released Monit 4.3 Beta 3, which contains
    these fixes. It can be downloaded at:
     <http://www.tildeslash.com/monit/beta/monit-4.3-beta3.tar.gz>
    http://www.tildeslash.com/monit/beta/monit-4.3-beta3.tar.gz
    MD5 Checksum:
    <http://www.tildeslash.com/monit/beta/monit-4.3-beta3.tar.gz.md5>
    http://www.tildeslash.com/monit/beta/monit-4.3-beta3.tar.gz.md5

    Vendor's official advisory can be found at:
    <http://www.tildeslash.com/monit/secadv_20040305.txt>
    http://www.tildeslash.com/monit/secadv_20040305.txt

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:mattmurphy@kc.rr.com>
    Matthew Murphy.

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