Security Update: [CSSA-2001-SCO.35] OpenServer: setcontext and sysi86 vulnerabilities

Type securityvulns
Reporter Securityvulns
Modified 2001-11-30T00:00:00



        Caldera International, Inc. Security Advisory

Subject: OpenServer: setcontext and sysi86 vulnerabilities Advisory number: CSSA-2001-SCO.35 Issue date: 2001 November 29 Cross reference:

  1. Problem Description

    This patch closes a family of security holes present in SCO
    OpenServer 5.0.6 and previous releases, which stem from the
    ability of regular user processes to reprogram segment
    descriptors and certain other CPU registers.
    Closing this family of security holes does, however, result in
    a functionality change which may prevent certain applications
    from running -- they will exit with an error, or dump core,
    instead of running properly.  For example, the i286emul and
    x286emul emulators will not work, so any '286 executables
    which require those emulators will not work.  It is our
    intention to enhance this patch in the future, such that it
    enables full functionality of such applications while still
    closing the security holes.
    If this patch breaks any crucial applications, the system
    administrator may choose to disable the patch, by editing the
    file /etc/conf/pack.d/kernel/space.c and setting the value of
    the allow_dscr_remap parameter to 1.  This will return the
    kernel to the old (not-secure) behavior.
  2. Vulnerable Versions

    Operating System        Version  Affected Files
    OpenServer              All



  1. Workaround

  2. OpenServer

4.1 Location of Fixed Binaries

4.2 Verification

    md5 checksums:

    89a6894b514d0175676d12745158aaea        VOL.000.000

    md5 is available for download from


4.3 Installing Fixed Binaries

    Upgrade the affected binaries with the following commands:

    Download the VOL.000.000 file to /tmp

    # custom

    Instruct custom to install from images, and supply /tmp as the
    directory of the VOL image.
  1. References

    This and other advisories are located at

    This advisory addresses Caldera Security internal incidents
    sr855993, sr855994, SCO-559-1328, SCO-559-1329, erg711906 and
  1. Disclaimer

    Caldera International, Inc. is not responsible for the misuse
    of any of the information we provide on our website and/or
    through our security advisories. Our advisories are a service
    to our customers intended to promote secure installation and
    use of Caldera International products.
  2. Acknowledgements

    Caldera wishes to thank the Last Stage of Delirium Research
    Group ( for their discovering of, and
    research into, these issues.