A (local) privilege escalation vulnerability as well as a mailbox ownership problem has been fixed in postfix. CVE-2008-2936 and CVE-2008-2937 have been assigned to this problem.

The remote Redhat Enterprise Linux 4 / 5 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2011:0422 advisory.

  - postfix improper mailbox permissions (CVE-2008-2937)

  - postfix: SMTP commands injection during plaintext to TLS session switch (CVE-2011-0411)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

It was discovered that Postfix did not flush the received SMTP commands buffer after switching to TLS encryption for an SMTP session.
A man-in-the-middle attacker could use this flaw to inject SMTP commands into a victim's session during the plain text phase. This would lead to those commands being processed by Postfix after TLS encryption is enabled, possibly allowing the attacker to steal the victim's mail or authentication credentials. (CVE-2011-0411)

It was discovered that Postfix did not properly check the permissions of users' mailbox files. A local attacker able to create files in the mail spool directory could use this flaw to create mailbox files for other local users, and be able to read mail delivered to those users.
(CVE-2008-2937)

After installing this update, the postfix service will be restarted automatically.

New upstream patch level version 2.5.5, including multiple security fixes detailed in upstream announcements:
http://www.postfix.org/announcements/20080814.html http://www.postfix.org/announcements/20080902.html

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

A (local) privilege escalation vulnerability as well as a mailbox ownership problem has been fixed in postfix. CVE-2008-2936 / CVE-2008-2937 have been assigned to this problem.

The remote host is affected by the vulnerability described in GLSA-200808-12 (Postfix: Local privilege escalation vulnerability)

    Sebastian Krahmer of SuSE has found that Postfix allows to deliver mail     to root-owned symlinks in an insecure manner under certain conditions.
    Normally, Postfix does not deliver mail to symlinks, except to     root-owned symlinks, for compatibility with the systems using symlinks     in /dev like Solaris. Furthermore, some systems like Linux allow to     hardlink a symlink, while the POSIX.1-2001 standard requires that the     symlink is followed. Depending on the write permissions and the     delivery agent being used, this can lead to an arbitrary local file     overwriting vulnerability (CVE-2008-2936). Furthermore, the Postfix     delivery agent does not properly verify the ownership of a mailbox     before delivering mail (CVE-2008-2937).
  Impact :

    The combination of these features allows a local attacker to hardlink a     root-owned symlink such that the newly created symlink would be     root-owned and would point to a regular file (or another symlink) that     would be written by the Postfix built-in local(8) or virtual(8)     delivery agents, regardless the ownership of the final destination     regular file. Depending on the write permissions of the spool mail     directory, the delivery style, and the existence of a root mailbox,     this could allow a local attacker to append a mail to an arbitrary file     like /etc/passwd in order to gain root privileges.
    The default configuration of Gentoo Linux does not permit any kind of     user privilege escalation.
    The second vulnerability (CVE-2008-2937) allows a local attacker,     already having write permissions to the mail spool directory which is     not the case on Gentoo by default, to create a previously nonexistent     mailbox before Postfix creates it, allowing to read the mail of another     user on the system.
  Workaround :

    The following conditions should be met in order to be vulnerable to     local privilege escalation.
    The mail delivery style is mailbox, with the Postfix built-in     local(8) or virtual(8) delivery agents.
    The mail spool directory (/var/spool/mail) is user-writeable.
    The user can create hardlinks pointing to root-owned symlinks     located in other directories.
    Consequently, each one of the following workarounds is efficient.
    Verify that your /var/spool/mail directory is not writeable by a     user. Normally on Gentoo, only the mail group has write access, and no     end-user should be granted the mail group ownership.
    Prevent the local users from being able to create hardlinks     pointing outside of the /var/spool/mail directory, e.g. with a     dedicated partition.
    Use a non-builtin Postfix delivery agent, like procmail or     maildrop.
    Use the maildir delivery style of Postfix ('home_mailbox=Maildir/'     for example).
    Concerning the second vulnerability, check the write permissions of     /var/spool/mail, or check that every Unix account already has a     mailbox, by using Wietse Venema's Perl script available in the official     advisory.

The remote Oracle Linux 5 host has packages installed that are affected by multiple vulnerabilities as referenced in the ELSA-2011-0422 advisory.

    - fix CVE-2011-0411 (#683387)
    - fix CVE-2008-2937 (#683387)

Tenable has extracted the preceding description block directly from the Oracle Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

A vulnerability has been found and corrected in postfix :

Postfix 2.5 before 2.5.4 and 2.6 before 2.6-20080814 delivers to a mailbox file even when this file is not owned by the recipient, which allows local users to read e-mail messages by creating a mailbox file corresponding to another user's account name (CVE-2008-2937).

This update provides a solution to this vulnerability.

Update :

Packages for 2008.0 are provided for Corporate Desktop 2008.0 customers

Updated postfix packages that fix two security issues are now available for Red Hat Enterprise Linux 4 and 5.

The Red Hat Security Response Team has rated this update as having moderate 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.

Postfix is a Mail Transport Agent (MTA), supporting LDAP, SMTP AUTH (SASL), and TLS.

It was discovered that Postfix did not flush the received SMTP commands buffer after switching to TLS encryption for an SMTP session.
A man-in-the-middle attacker could use this flaw to inject SMTP commands into a victim's session during the plain text phase. This would lead to those commands being processed by Postfix after TLS encryption is enabled, possibly allowing the attacker to steal the victim's mail or authentication credentials. (CVE-2011-0411)

It was discovered that Postfix did not properly check the permissions of users' mailbox files. A local attacker able to create files in the mail spool directory could use this flaw to create mailbox files for other local users, and be able to read mail delivered to those users.
(CVE-2008-2937)

Red Hat would like to thank the CERT/CC for reporting CVE-2011-0411, and Sebastian Krahmer of the SuSE Security Team for reporting CVE-2008-2937. The CERT/CC acknowledges Wietse Venema as the original reporter of CVE-2011-0411.

Users of Postfix are advised to upgrade to these updated packages, which contain backported patches to resolve these issues. After installing this update, the postfix service will be restarted automatically.

ID	Name	Product	Family	Published	Updated	Severity
40111	openSUSE Security Update : postfix (postfix-133)	Nessus	SuSE Local Security Checks	7/21/2009	1/14/2021	medium
53310	RHEL 4 / 5 : postfix (RHSA-2011:0422)	Nessus	Red Hat Local Security Checks	4/7/2011	4/27/2024	critical
33897	openSUSE 10 Security Update : postfix (postfix-5501)	Nessus	SuSE Local Security Checks	8/15/2008	1/14/2021	medium
61010	Scientific Linux Security Update : postfix on SL4.x, SL5.x i386/x86_64	Nessus	Scientific Linux Local Security Checks	8/1/2012	1/14/2021	medium
34376	Fedora 9 : postfix-2.5.5-1.fc9 (2008-8593)	Nessus	Fedora Local Security Checks	10/10/2008	1/11/2021	medium
33888	SuSE 10 Security Update : Postfix (ZYPP Patch Number 5500)	Nessus	SuSE Local Security Checks	8/14/2008	1/14/2021	medium
33891	GLSA-200808-12 : Postfix: Local privilege escalation vulnerability	Nessus	Gentoo Local Security Checks	8/15/2008	1/6/2021	medium
68248	Oracle Linux 5 : post (ELSA-2011-0422)	Nessus	Oracle Linux Local Security Checks	7/12/2013	10/22/2024	critical
40813	Mandriva Linux Security Advisory : postfix (MDVSA-2009:224-1)	Nessus	Mandriva Local Security Checks	8/31/2009	1/6/2021	low
34377	Fedora 8 : postfix-2.5.5-1.fc8 (2008-8595)	Nessus	Fedora Local Security Checks	10/10/2008	1/11/2021	medium
41231	SuSE9 Security Update : Postfix (YOU Patch Number 12219)	Nessus	SuSE Local Security Checks	9/24/2009	1/14/2021	medium
53338	CentOS 4 / 5 : postfix (CESA-2011:0422)	Nessus	CentOS Local Security Checks	4/11/2011	1/4/2021	medium

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