RHSA-2010:0872 - Security Advisory

Topic

Updated glibc packages that fix two security issues and two bugs are now
available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having
important security impact. Common Vulnerability Scoring System (CVSS) base
scores, which give detailed severity ratings, are available for each
vulnerability from the CVE links in the References section.

Description

The glibc packages contain the standard C libraries used by multiple
programs on the system. These packages contain the standard C and the
standard math libraries. Without these two libraries, a Linux system
cannot function properly.

It was discovered that the glibc dynamic linker/loader did not handle the
$ORIGIN dynamic string token set in the LD_AUDIT environment variable
securely. A local attacker with write access to a file system containing
setuid or setgid binaries could use this flaw to escalate their privileges.
(CVE-2010-3847)

It was discovered that the glibc dynamic linker/loader did not perform
sufficient safety checks when loading dynamic shared objects (DSOs) to
provide callbacks for its auditing API during the execution of privileged
programs. A local attacker could use this flaw to escalate their privileges
via a carefully-chosen system DSO library containing unsafe constructors.
(CVE-2010-3856)

Red Hat would like to thank Tavis Ormandy for reporting the CVE-2010-3847
issue, and Ben Hawkes and Tavis Ormandy for reporting the CVE-2010-3856
issue.

This update also fixes the following bugs:

• Previously, the generic implementation of the strstr() and memmem()

functions did not handle certain periodic patterns correctly and could find
a false positive match. This error has been fixed, and both functions now
work as expected. (BZ#643341)

• The "TCB_ALIGNMENT" value has been increased to 32 bytes to prevent

applications from crashing during symbol resolution on 64-bit systems with
support for Intel AVX vector registers. (BZ#643343)

All users are advised to upgrade to these updated packages, which contain
backported patches to correct these issues.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/kb/docs/DOC-11259

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

• BZ - 643306 - CVE-2010-3847 glibc: ld.so insecure handling of $ORIGIN in LD_AUDIT for setuid/setgid programs
• BZ - 643341 - memmem, strstr, and strcasestr are broken
• BZ - 643343 - [Intel 6.0 Bug] Dynamic linker failed to align TCB for AVX
• BZ - 645672 - CVE-2010-3856 glibc: ld.so arbitrary DSO loading via LD_AUDIT in setuid/setgid programs

CVEs

• CVE-2010-3847
• CVE-2010-3856

References

• http://www.redhat.com/security/updates/classification/#important