Latest Linux Vulnerabilities Get Patches

By Larry Seltzer  |  Posted 2004-10-21 Print this article Print

Graphics library and kernel functions are open to attack, but the current Linux kernel addresses the problems.

A series of recently announced security flaws open Linux and related technologies to attacks ranging from denials of service and local exploits to the potential for remote system compromise. Senior Linux developer Alan Cox announced a set of "race conditions" in the Linux kernel that were fixed in Version 2.6.9. The problems are in the terminal subsystem. Patches are also available for the 2.4x kernel, but not the 2.2 kernel.

Cox reports two problems, the first involving a local program performing specific operations with a particular timing, resulting in crashes and "other undefined behavior," including the release of small amounts of random kernel data. The second attack involves dial-up users connecting over PPP (point-to-point protocol) ports and performing a console switch at precisely the right time, causing a crash. The second attack can only be reproduced over direct serial lines, not modems, leading Cox to minimize the possibility of a true remote attack.

A separate problem was reported in the iptables program of the 2.6x kernel, specifically an integer underflow. iptables is part of the Linux kernels network security. Along with netfilter it provides packet filtering, network address translation and other security features.

The integer underflow, the exact nature of which has not yet been revealed, is alleged to occur in iptables logging when both IP and TCP options are enabled. According to a SuSE write-up on the problem, the attacker would have to hand-construct an IP packet. The problem is fixed in the 2.6.8 version of the kernel.

In the same advisory SuSE also credits IBM with finding a local root exploit in its own SuSE Linux Enterprise Server 9 on the S/390 platform. This problem results from incorrect handling of a privileged instruction.

For insights on security coverage around the Web, check out Security Center Editor Larry Seltzers Weblog. Finally, the LibPNG graphics library, popular in most distributions of Linux and many applications, such as Mozilla, is reported to contain several integer overflows. Theoretically these could allow a specially crafted PNG image to cause arbitrary code to be executed, but this has not yet been demonstrated.

LibPNG is the official library for handling Portable Network Graphics (PNG) files. A new library version is available to address the problem, but since LibPNG is linked into many applications, users may need to get updates from application vendors.

Check out eWEEK.coms Security Center for the latest security news, reviews and analysis.

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Larry Seltzer has been writing software for and English about computers ever since—,much to his own amazement—,he graduated from the University of Pennsylvania in 1983.

He was one of the authors of NPL and NPL-R, fourth-generation languages for microcomputers by the now-defunct DeskTop Software Corporation. (Larry is sad to find absolutely no hits on any of these +products on Google.) His work at Desktop Software included programming the UCSD p-System, a virtual machine-based operating system with portable binaries that pre-dated Java by more than 10 years.

For several years, he wrote corporate software for Mathematica Policy Research (they're still in business!) and Chase Econometrics (not so lucky) before being forcibly thrown into the consulting market. He bummed around the Philadelphia consulting and contract-programming scenes for a year or two before taking a job at NSTL (National Software Testing Labs) developing product tests and managing contract testing for the computer industry, governments and publication.

In 1991 Larry moved to Massachusetts to become Technical Director of PC Week Labs (now eWeek Labs). He moved within Ziff Davis to New York in 1994 to run testing at Windows Sources. In 1995, he became Technical Director for Internet product testing at PC Magazine and stayed there till 1998.

Since then, he has been writing for numerous other publications, including Fortune Small Business, Windows 2000 Magazine (now Windows and .NET Magazine), ZDNet and Sam Whitmore's Media Survey.

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