Security

See CERT Advisory CA-2003-07 for additional information.

In addition to the above problem the tcpdump developers discovered a potential infinite loop when parsing malformed BGP packets. They also discovered a buffer overflow that can be exploited with certain malformed NFS packets.

A remote root vulnerability in slave setups and some buffer overflows in the network information server code were discovered by the apcupsd developers. They have been fixed in the latest unstable version, 3.10.5 which contains additional enhancements like USB support, and the latest stable version, 3.8.6.

There are a few changes that need to be noted, such as the port has changed from port 7000 to post 3551 for NIS, and the new config only allows access from the localhost. Users may need to modify their configuration files appropriately, depending upon their configuration.

Red Hat has sent out an alert (not a regular advisory) suggesting that customers apply its previous BIND updates, which upgrade the system to BIND9.

Unfortunatly that does not mean that Linux systems are not vulnerable. Similar code, without Olaf Firch's fixes, is in the glibc getnetbyXXX functions. These functions are described in the SuSE alert as " used by very few applications only, such as ifconfig and ifuser, which makes exploits less likely."

CERT Advisory: CA-2002-19 Buffer Overflow in Multiple DNS Resolver Libraries

CAN-2002-0651
CAN-2002-0684

A denial of service vulnerability exists in BitchX. Sending a malformed RPL_NAMREPLY numeric 353 causes BitchX to segfault. This problem was reported to panasync@efnet#bitchx on Jan 30 2003, as of this writing we are unaware of any patches or workarounds provided by panasync and or any members of #bitchx

A buffer overflow bug in the Canna server up to and including version 3.5b2 allows a local user to gain the privileges of the user 'bin' which could lead to further exploits. The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CAN-2002-1158 to this issue.

A lack of validation of requests has been found that affects Canna version 3.6 and earlier. A malicious remote user could exploit this vulnerability to leak information, or cause a denial of service attack. (CAN-2002-1159)

See also http://canna.sourceforge.jp/sec/Canna-2002-01.txt

CAN-2002-1158
CAN-2002-1159

On servers which are configured to allow anonymous read-only access, this bug could be used by anonymous users to gain write privileges. Users with CVS write privileges can then use the Update-prog and Checkin-prog features to execute arbitrary commands on the server.

All users of CVS are advised to upgrade to erratum packages which contain patches to correct the double-free bug.

See also this CERT advisory

When the dhcp-relay receives a BOOTP request it forwards the request to the DHCP server using the broadcast MAC address ff:ff:ff:ff:ff:ff which causes the network interface to reflect the packet back into the socket. To prevent loops the dhcrelay checks whether the relay-address is its own, in which case the packet would be dropped. In combination with a missing upper boundary for the hop counter an attacker can force the dhcp-relay to send a continuing packet storm towards the configured dhcp server(s).

This patch introduces a new commandline switch ``-c maxcount'' and people are advised to start the dhcp-relay with ``dhcrelay -c 10'' or a smaller number, which will only create that many packets.

The dhcrelay program from the ``dhcp'' package does not seem to be affected since DHCP packets are dropped if they were apparently relayed already.

Updating as soon as practical is a good idea.

CERT/CC Vulnerability Note VU#192995 Integer overflow in xdr_array() function when deserializing the XDR stream

The BIND 4 and BIND 8.2.x stub resolver libraries, and other libraries such as glibc 2.2.5 and earlier, libc, and libresolv, uses the maximum buffer size instead of the actual size when processing a DNS response, which causes the stub resolvers to read past the actual boundary ("read buffer overflow"), allowing remote attackers to cause a denial of service (crash).

An attacker could craft a long filename for an attachment that would overflow two buffers when a certain option for interactive use was given, opening the possibility to inject arbitrary code. This code would then be executed under the user id hypermail runs as, mostly as a local user. Automatic and silent use of hypermail does not seem to be affected.

The CGI program mail, which is not installed by the Debian package, does a reverse look-up of the user's IP number and copies the resulting hostname into a fixed-size buffer. A specially crafted DNS reply could overflow this buffer, opening the program to an exploit.

1. The impwagent program creates a temporary directory in an insecure manner in /tmp using predictable directory names without checking the return code of mkdir, so it's possible to seize a permission of the temporary directory by local access as another user.

2. The immknmz program creates a temporary file in an insecure manner in /tmp using a predictable filename, so an attacker with local access can easily create and overwrite files as another user.

The uml_net utility in kernel-utils packages with Red Hat Linux 8.0 was incorrectly shipped setuid root. This could allow local users to control certain network interfaces, add and remove arp entries and routes, and put interfaces in and out of promiscuous mode.

All users of the kernel-utils package should update to these packages that contain a version of uml_net that is not setuid root.

Alternatively, as a work-around to this vulnerability issue the following command as root:

chmod -s /usr/bin/uml_net

Another vulnerability is due to the way libmcrypt loads algorithms via libtool. When the algorithms are loaded dynamically the each time the algorithm is loaded a small (few kilobytes) of memory are leaked. In a persistant enviroment (web server) this could lead to a memory exhaustion attack that will exhaust all avaliable memory by launching repeated requests at an application utilizing the mcrypt library.

CAN-2002-1405

Note that mail processing programs which use this package can be affected by this vulnerability; in particular, SpamAssassin is vulnerable if you use the -r or -w flags.

Read the the full advisory for the details.

Note that falconseye does not contain the file permission error CAN-2003-0359 which affected some other nethack packages.

Andreas Beck discovered that versions of pam_xauth supplied with Red Hat Linux since version 7.1 would forward authorization information from the root account to unprivileged users. This could be used by a local attacker to gain access to an administrator's X session. In order to exploit this vulnerability, the attacker would have to get the administrator, as root, to use su to the account belonging to the attacker.

CAN-2002-0985
CAN-2002-0986

CAN-2002-1119

When creating a user account, the version of useradd included in Red Hat Linux 7.2, 7.3, and 8.0 creates a mailbox file with incorrectly-set group ownership. Instead of setting the file's group ownership to the 'mail' group, it is set to the user's primary group.

On systems where other users share the same primary group, this would allow those users to be able to read and write other user mailboxes.

"Due to a remotely exploitable security hole being discovered that effects all previous Webmin releases, version 1.070 is now available for download from http://www.webmin.com/ and mirror sites. This problem was reported by Cintia M. Imanishi, but fortunately there have been no known malicious exploits of it yet. However, all users should upgrade to 1.070 as soon as possible."

"Also available is Usermin 1.000 which fixes the exact same security hole. It includes the same File Manager features, as well as support for IMAP folders and an IMAP inbox in the Read Mail module."

Read this alert for the details.

The VNC server acts as an X server, but the script for starting it generates an MIT X cookie (which is used for X authentication) without using a strong enough random number generator. This could allow an attacker to be able to more easily guess the authentication cookie.

The VNC DES authentication scheme is implemented using a challenge-response architecture, producing a random and different challenge for each authentication attempt. A bug in the function for generating the random challenge caused the random seed to get reset to the current time on every authentication attempt. Therefore, two authentication attempts within the same second could receive the same challenge. An eavesdropper could exploit this vulnerability by replaying the response, thereby gaining authentication.

All users of VNC are advised to upgrade to these erratum packages, which contain patches to correct these issues.

FTP clients must check to see if an FTP server's response to the NLST command includes any directory information along with the list of filenames required by the FTP protocol (RFC 959, section 4.1.3).

If the FTP client fails to do so, a malicious FTP server can send filenames beginning with '/' or containing '/../' which can be used to direct a vulnerable FTP client to write files (such as .forward, .rhosts, .shosts, etc.) that can then be used for later attacks against the client machine.

See also this Bugtraq article from 1997.

CAN-2002-1344