FreeBSD libkvm could leak sensitive file descriptors and disclose kernel memory

bsd-libkvm-descriptor-leak (10109) The risk level is classified as MediumMedium Risk


FreeBSDcould allow a local attacker to gain sensitive information, caused by a vulnerability in the kvm(3) library (libkvm). A local attacker could use the asmon, ascpu, bubblemon, wmmon, or wmnet2 FreeBSD Ports Collection application to start other applications and cause these applications to leak /dev/mem and /dev/kmem file descriptors. These applications could then be used by an attacker to read kernel memory, which would allow the attacker to obtain sensitive information. This information could be used to launch further attacks against the affected system and possibly be leveraged to obtain root privileges.


Obtain Information


For FreeBSD:
Upgrade to the latest version of FreeBSD (4.6-STABLE or later) or to the RELENG_4_6, RELENG_4_5, or RELENG_4_4 security branch dated later than 2002-09-13, as listed in FreeBSD Security Advisory FreeBSD-SA-02:39.libkvm. See References.


Apply the appropriate patch for your system, as listed in FreeBSD Security Advisory FreeBSD-SA-02:39.libkvm. See References.

As a workaround, remove the setgid bit on the affected applications.

For other distributions:
Contact your vendor for upgrade or patch information.


  • FreeBSD Security Advisory FreeBSD-SA-02:39.libkvm: Applications using libkvm may leak sensitive descriptors.
  • iDEFENSE Security Advisory 09.16.2002 : FreeBSD Ports libkvm Security Vulnerabilities. (From Neohapsis archive)
  • BID-5714: BubbleMon Kernel Memory File Descriptor Leakage Vulnerability
  • BID-5716: ASCPU Kernel Memory File Descriptor Leakage Vulnerability
  • BID-5718: WMMon Memory Character File Open File Descriptor Read Vulnerability
  • BID-5719: WMNet2 Kernel Memory File Descriptor Leakage Vulnerability
  • BID-572: ToxSoft NextFTP Buffer Overflow Vulnerability
  • BID-5720: ASMon Kernel Memory File Descriptor Leakage Vulnerability
  • CVE-2002-1125: FreeBSD port programs that use libkvm for FreeBSD 4.6.2-RELEASE and earlier, including (1) asmon, (2) ascpu, (3) bubblemon, (4) wmmon, and (5) wmnet2, leave open file descriptors for /dev/mem and /dev/kmem, which allows local users to read kernel memory.
  • OSVDB ID: 6097: FreeBSD libkvm Open File Descriptor Memory Read

Platforms Affected:

  • FreeBSD FreeBSD 4.0
  • FreeBSD FreeBSD 4.1
  • FreeBSD FreeBSD 4.2
  • FreeBSD FreeBSD 4.3
  • FreeBSD FreeBSD 4.4
  • FreeBSD FreeBSD 4.5
  • FreeBSD FreeBSD 4.6
  • FreeBSD FreeBSD 4.6.1
  • FreeBSD FreeBSD 4.6.2


Sep 16, 2002

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