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Debian DSA-956-1 : lsh-server - filedescriptor leak

low Nessus Plugin ID 22822

Synopsis

The remote Debian host is missing a security-related update.

Description

Stefan Pfetzing discovered that lshd, a Secure Shell v2 (SSH2) protocol server, leaks a couple of file descriptors, related to the randomness generator, to user shells which are started by lshd. A local attacker can truncate the server's seed file, which may prevent the server from starting, and with some more effort, maybe also crack session keys.

After applying this update, you should remove the server's seed file (/var/spool/lsh/yarrow-seed-file) and then regenerate it with 'lsh-make-seed --server' as root.

For security reasons, lsh-make-seed really needs to be run from the console of the system you are running it on. If you run lsh-make-seed using a remote shell, the timing information lsh-make-seed uses for its random seed creation is likely to be screwed. If need be, you can generate the random seed on a different system than that which it will eventually be on, by installing the lsh-utils package and running 'lsh-make-seed -o my-other-server-seed-file'. You may then transfer the seed to the destination system as using a secure connection.

The old stable distribution (woody) may not be affected by this problem.

Solution

Upgrade the lsh-server package.

For the stable distribution (sarge) this problem has been fixed in version 2.0.1-3sarge1.

See Also

http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=349303

http://www.debian.org/security/2006/dsa-956

Plugin Details

Severity: Low

ID: 22822

File Name: debian_DSA-956.nasl

Version: 1.17

Type: local

Agent: unix

Published: 10/14/2006

Updated: 1/4/2021

Supported Sensors: Agentless Assessment, Continuous Assessment, Frictionless Assessment Agent, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5.2

CVSS v2

Risk Factor: Low

Base Score: 3.6

Vector: CVSS2#AV:L/AC:L/Au:N/C:P/I:N/A:P

Vulnerability Information

CPE: p-cpe:/a:debian:debian_linux:lsh-utils, cpe:/o:debian:debian_linux:3.1

Required KB Items: Host/local_checks_enabled, Host/Debian/release, Host/Debian/dpkg-l

Patch Publication Date: 1/26/2006

Vulnerability Publication Date: 1/20/2006

Reference Information

CVE: CVE-2006-0353

DSA: 956