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Category:   OS (Linux)  >   Linux Kernel Vendors:
Linux 2.4 Kernel /proc/tty/driver/serial May Disclose Password Characteristics to Local Users
SecurityTracker Alert ID:  1007243
SecurityTracker URL:
CVE Reference:   CVE-2003-0461   (Links to External Site)
Updated:  May 12 2004
Original Entry Date:  Jul 22 2003
Impact:   Disclosure of authentication information
Vendor Confirmed:  Yes  
Version(s): 2.4.20
Description:   An information disclosure vulnerability was reported in the Linux 2.4 kernel. A flaw in '/proc/tty/driver/serial' may let local users gain information about password characteristics.

It is reported that '/proc/tty/driver/serial discloses the exact character counts for information on the serial links. A local user can monitor this object to attempt to determine the length of a target user's password (as typed) and keystroke timing, which can yield information about the target user's password.

Impact:   A local user may be able to obtain information about password lengths and password keystroke timing.
Solution:   It is not clear if an upstream fix is available yet. Fixes for individual kernel distributions are pending. Check the Message History for fixes from various kernel vendors.
Vendor URL: (Links to External Site)
Cause:   Access control error

Message History:   This archive entry has one or more follow-up message(s) listed below.
Jul 22 2003 (Red Hat Issues Fix) Linux 2.4 Kernel /proc/tty/driver/serial May Disclose Password Characteristics to Local Users
The vendor has released a fix.
May 12 2004 (Red Hat Issues Fix for RH Enterprise Linux) Linux 2.4 Kernel /proc/tty/driver/serial May Disclose Password Characteristics to Local Users
Red Hat has released a fix for Red Hat Enterprise Linux 3.

 Source Message Contents

Subject:  Linux 2.4 Kernel Vulnerabilities

Red Hat reported the following security vulnerabilities in the Linux 2.4 Kernel:

CAN-2003-0461: /proc/tty/driver/serial reveals the exact character counts
for serial links.  This could be used by a local attacker to infer password
lengths and inter-keystroke timings during password entry.

CAN-2003-0462: Paul Starzetz discovered a file read race condition existing
in the execve() system call, which could cause a local crash.

CAN-2003-0464: A recent change in the RPC code set the reuse flag on
newly-created sockets.  Olaf Kirch noticed that his could allow normal
users to bind to UDP ports used for services such as nfsd.

CAN-2003-0476: The execve system call in Linux 2.4.x records the file
descriptor of the executable process in the file table of the calling
process, allowing local users to gain read access to restricted file

CAN-2003-0501: The /proc filesystem in Linux allows local users to obtain
sensitive information by opening various entries in /proc/self before
executing a setuid program.  This causes the program to fail to change the
ownership and permissions of already opened entries.

CAN-2003-0550: The STP protocol is known to have no security, which could
allow attackers to alter the bridge topology.  STP is now turned off by

CAN-2003-0551: STP input processing was lax in its length checking, which
could lead to a denial of service.

CAN-2003-0552: Jerry Kreuscher discovered that the Forwarding table could
be spoofed by sending forged packets with bogus source addresses the same
as the local host.

Red Hat issued fixed versions based on the 2.4.20 kernel.  It is not clear which upstream 
kernel version(s) contain these fixes.  See the Red Hat advisory RHSA-2003:238-01 for 
information on the Red Hat fixes.


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