VNC rand() generates weak cookies
| vnc-rand-weak-cookie (11384) |  Medium Risk |
Description:
The server wrapper in VNC versions prior to 3.3.3r2-21 uses the rand() function, instead of the srand() function, which causes the server to generate weaker than expected cookies. A remote attacker could use this vulnerability to guess a user's authentication cookie and gain unauthorized access to the system.
Consequences:
Configuration
Remedy:
Upgrade to the latest version of VNC (3.3.6 or later), available from the VNC Web page. See References.
For Red Hat Linux:
Upgrade to the latest vnc package, as listed below. Refer to RHSA-2003:041-15 for more information. See References.
Red Hat 7.0, 7.1, and 7.2: 3.3.3r2-18.6 or later
Red Hat 7.1 for iSeries and pSeries: 3.3r2-18.6.0p or later
Red Hat 7.3: 3.3.3r2-28.2. or later
Red Hat 8.0: 3.3.3r2-39.2 or later
For Gentoo Linux containing the tighevnc package:
Upgrade to the latest version of tightvnc(1.2.8 or later), as listed in Gentoo Linux Security Announcement 200302-15. See References.
For Gentoo Linux containing the net-misc/vnc package:
Upgrade to the latest version of vnc (3.3.6-r1 or later), as listed in Gentoo Linux Security Announcement 200302-16. See References.
For Mandrake Linux:
Upgrade to the latest vnc package, as listed below. Refer to MandrakeSoft Security Advisory MDKSA-2003:022:vnc for more information. See References.
Mandrake Linux 7.2: 3.3.3-8.4mdk or later
Mandrake Linux 8.0, 8.1, and 8.2: 3.3.3r2-9.3mdk or later
Mandrake Linux 9.0: 1.2.5-2.3mdk or later
For Conectiva Linux:
Upgrade to the latest vnc package, as listed below. Refer to Conectiva Linux Security Announcement CLSA-2003:640 for more information. See References.
Conectiva Linux 7.0: 3.3.3-6U70_2cl or later
Conectiva Linux 8.0: 3.3.3r2+tight1.2.2-6U80_1cl or later
For Sun Linux 5.0:
Apply the appropriate patches when they become available, as listed in Sun Alert ID: 56161. See References.
For other distributions:
Contact your vendor for upgrade or patch information.
References:
- CIAC Information Bulletin N-140: Sun Linux Vulnerability in VNC Package may allow local or remote unauthorized access.
- Conectiva Linux Security Announcement CLSA-2003:640: Vulnerabilties in cookies and random challenge generations.
- Gentoo Linux Security Announcement 200302-15: tightvnc -- insecure cookie generation.
- Gentoo Linux Security Announcement 200302-16: vnc -- insecure cookie generation.
- Sun Alert ID: 56161: Sun Linux Vulnerability in VNC Package May Allow Local or Remote Unauthorized Access.
- VNC Changelog Web site: http://changelogs.credativ.org/debian/pool/main/v/vnc/vnc_3.3.6-3/changelog.
- VNC Web site: VNC - Virtual Network Computing from AT&T Labratories Cambridge.
- BID-6905: TightVNC Server Authentication Cookie Predictability Vulnerability
- CVE-2002-1511: The vncserver wrapper for vnc before 3.3.3r2-21 uses the rand() function instead of srand(), which causes vncserver to generate weak cookies.
- MDKSA-2003:022: Updated vnc packages fix cookie vulnerability
- RHSA-2003-041: Updated VNC packages fix replay and cookie vulnerabilities
- RHSA-2003-068: vnc security update
Platforms Affected:
- AT&T VNC prior to 3.3.3r2-21
- Conectiva Linux 7.0
- Conectiva Linux 8.0
- Gentoo Linux
- MandrakeSoft Mandrake Linux 7.2
- MandrakeSoft Mandrake Linux 8.0
- MandrakeSoft Mandrake Linux 8.0 PPC
- MandrakeSoft Mandrake Linux 8.1
- MandrakeSoft Mandrake Linux 8.2
- MandrakeSoft Mandrake Linux 8.2 PPC
- MandrakeSoft Mandrake Linux 9.0
- RedHat Enterprise Linux 2.1 AS
- RedHat Linux 7
- RedHat Linux 7.1
- RedHat Linux 7.1 for iSeries
- RedHat Linux 7.1 for pSeries
- RedHat Linux 7.2
- RedHat Linux 7.3
- RedHat Linux 8.0
- Sun Linux 5.0
Reported:
Oct 11, 2002
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