The check_acl function in pam_xauth.c in the pam_xauth module in Linux-PAM (aka pam) 1.1.2 and earlier does not verify that a certain ACL file is a regular file, which might allow local users to cause a denial of service (resource consumption) via a special file.

The remote Redhat Enterprise Linux 4 host has one or more packages installed that are affected by multiple vulnerabilities that have been acknowledged by the vendor but will not be patched.

  - pam: pam_env and pam_mail accessing users' file with root privileges (CVE-2010-3435)

  - pam: pam_xauth: Does not check if certain ACL file is a regular file (CVE-2010-4707)

  - The run_coprocess function in pam_xauth.c in the pam_xauth module in Linux-PAM (aka pam) before 1.1.2 does     not check the return values of the setuid, setgid, and setgroups system calls, which might allow local     users to read arbitrary files by executing a program that relies on the pam_xauth PAM check.
    (CVE-2010-3316)

Note that Nessus has not tested for these issues but has instead relied on the package manager's report that the package is installed.

From Red Hat Security Advisory 2010:0891 :

Updated pam packages that fix three security issues are now available for Red Hat Enterprise Linux 6.

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.

Pluggable Authentication Modules (PAM) provide a system whereby administrators can set up authentication policies without having to recompile programs that handle authentication.

It was discovered that the pam_namespace module executed the external script namespace.init with an unchanged environment inherited from an application calling PAM. In cases where such an environment was untrusted (for example, when pam_namespace was configured for setuid applications such as su or sudo), a local, unprivileged user could possibly use this flaw to escalate their privileges. (CVE-2010-3853)

It was discovered that the pam_env and pam_mail modules used root privileges while accessing user's files. A local, unprivileged user could use this flaw to obtain information, from the lines that have the KEY=VALUE format expected by pam_env, from an arbitrary file.
Also, in certain configurations, a local, unprivileged user using a service for which the pam_mail module was configured for, could use this flaw to obtain limited information about files or directories that they do not have access to. (CVE-2010-3435)

Note: As part of the fix for CVE-2010-3435, this update changes the default value of pam_env's configuration option user_readenv to 0, causing the module to not read user's ~/.pam_environment configuration file by default, as reading it may introduce unexpected changes to the environment of the service using PAM, or PAM modules consulted after pam_env.

It was discovered that the pam_xauth module did not verify the return values of the setuid() and setgid() system calls. A local, unprivileged user could use this flaw to execute the xauth command with root privileges and make it read an arbitrary input file.
(CVE-2010-3316)

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for reporting the CVE-2010-3435 issue.

All pam users should upgrade to these updated packages, which contain backported patches to correct these issues.

From Red Hat Security Advisory 2010:0819 :

Updated pam packages that fix three security issues are now available for Red Hat Enterprise Linux 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.

Pluggable Authentication Modules (PAM) provide a system whereby administrators can set up authentication policies without having to recompile programs that handle authentication.

It was discovered that the pam_namespace module executed the external script namespace.init with an unchanged environment inherited from an application calling PAM. In cases where such an environment was untrusted (for example, when pam_namespace was configured for setuid applications such as su or sudo), a local, unprivileged user could possibly use this flaw to escalate their privileges. (CVE-2010-3853)

It was discovered that the pam_mail module used root privileges while accessing users' files. In certain configurations, a local, unprivileged user could use this flaw to obtain limited information about files or directories that they do not have access to.
(CVE-2010-3435)

It was discovered that the pam_xauth module did not verify the return values of the setuid() and setgid() system calls. A local, unprivileged user could use this flaw to execute the xauth command with root privileges and make it read an arbitrary input file.
(CVE-2010-3316)

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for reporting the CVE-2010-3435 issue.

All pam users should upgrade to these updated packages, which contain backported patches to correct these issues.

The remote host is affected by the vulnerability described in GLSA-201206-31 (Linux-PAM: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in Linux-PAM. Please       review the CVE identifiers referenced below for details.
  Impact :

    A local attacker could use specially crafted files to cause a buffer       overflow, possibly resulting in privilege escalation or Denial of       Service. Furthermore, a local attacker could execute specially crafted       programs or symlink attacks, possibly resulting in data loss or       disclosure of sensitive information.
  Workaround :

    There is no known workaround at this time.

USN-1140-1 fixed vulnerabilities in PAM. A regression was found that caused cron to stop working with a 'Module is unknown' error. As a result, systems configured with automatic updates will not receive updates until cron is restarted, these updates are installed or the system is rebooted. This update fixes the problem.

We apologize for the inconvenience.

Marcus Granado discovered that PAM incorrectly handled configuration files with non-ASCII usernames. A remote attacker could use this flaw to cause a denial of service, or possibly obtain login access with a different users username. This issue only affected Ubuntu 8.04 LTS.
(CVE-2009-0887)

It was discovered that the PAM pam_xauth, pam_env and pam_mail modules incorrectly handled dropping privileges when performing operations. A local attacker could use this flaw to read certain arbitrary files, and access other sensitive information. (CVE-2010-3316, CVE-2010-3430, CVE-2010-3431, CVE-2010-3435)

It was discovered that the PAM pam_namespace module incorrectly cleaned the environment during execution of the namespace.init script. A local attacker could use this flaw to possibly gain privileges. (CVE-2010-3853)

It was discovered that the PAM pam_xauth module incorrectly handled certain failures. A local attacker could use this flaw to delete certain unintended files. (CVE-2010-4706)

It was discovered that the PAM pam_xauth module incorrectly verified certain file properties. A local attacker could use this flaw to cause a denial of service. (CVE-2010-4707).

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

Marcus Granado discovered that PAM incorrectly handled configuration files with non-ASCII usernames. A remote attacker could use this flaw to cause a denial of service, or possibly obtain login access with a different users username. This issue only affected Ubuntu 8.04 LTS.
(CVE-2009-0887)

It was discovered that the PAM pam_xauth, pam_env and pam_mail modules incorrectly handled dropping privileges when performing operations. A local attacker could use this flaw to read certain arbitrary files, and access other sensitive information. (CVE-2010-3316, CVE-2010-3430, CVE-2010-3431, CVE-2010-3435)

It was discovered that the PAM pam_namespace module incorrectly cleaned the environment during execution of the namespace.init script.
A local attacker could use this flaw to possibly gain privileges.
(CVE-2010-3853)

It was discovered that the PAM pam_xauth module incorrectly handled certain failures. A local attacker could use this flaw to delete certain unintended files. (CVE-2010-4706)

It was discovered that the PAM pam_xauth module incorrectly verified certain file properties. A local attacker could use this flaw to cause a denial of service. (CVE-2010-4707).

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

Updated pam packages that fix three security issues are now available for Red Hat Enterprise Linux 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.

Pluggable Authentication Modules (PAM) provide a system whereby administrators can set up authentication policies without having to recompile programs that handle authentication.

It was discovered that the pam_namespace module executed the external script namespace.init with an unchanged environment inherited from an application calling PAM. In cases where such an environment was untrusted (for example, when pam_namespace was configured for setuid applications such as su or sudo), a local, unprivileged user could possibly use this flaw to escalate their privileges. (CVE-2010-3853)

It was discovered that the pam_mail module used root privileges while accessing users' files. In certain configurations, a local, unprivileged user could use this flaw to obtain limited information about files or directories that they do not have access to.
(CVE-2010-3435)

It was discovered that the pam_xauth module did not verify the return values of the setuid() and setgid() system calls. A local, unprivileged user could use this flaw to execute the xauth command with root privileges and make it read an arbitrary input file.
(CVE-2010-3316)

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for reporting the CVE-2010-3435 issue.

All pam users should upgrade to these updated packages, which contain backported patches to correct these issues.

Updated pam packages that fix three security issues are now available for Red Hat Enterprise Linux 6.

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.

Pluggable Authentication Modules (PAM) provide a system whereby administrators can set up authentication policies without having to recompile programs that handle authentication.

It was discovered that the pam_namespace module executed the external script namespace.init with an unchanged environment inherited from an application calling PAM. In cases where such an environment was untrusted (for example, when pam_namespace was configured for setuid applications such as su or sudo), a local, unprivileged user could possibly use this flaw to escalate their privileges. (CVE-2010-3853)

It was discovered that the pam_env and pam_mail modules used root privileges while accessing user's files. A local, unprivileged user could use this flaw to obtain information, from the lines that have the KEY=VALUE format expected by pam_env, from an arbitrary file.
Also, in certain configurations, a local, unprivileged user using a service for which the pam_mail module was configured for, could use this flaw to obtain limited information about files or directories that they do not have access to. (CVE-2010-3435)

Note: As part of the fix for CVE-2010-3435, this update changes the default value of pam_env's configuration option user_readenv to 0, causing the module to not read user's ~/.pam_environment configuration file by default, as reading it may introduce unexpected changes to the environment of the service using PAM, or PAM modules consulted after pam_env.

It was discovered that the pam_xauth module did not verify the return values of the setuid() and setgid() system calls. A local, unprivileged user could use this flaw to execute the xauth command with root privileges and make it read an arbitrary input file.
(CVE-2010-3316)

Red Hat would like to thank Sebastian Krahmer of the SuSE Security Team for reporting the CVE-2010-3435 issue.

All pam users should upgrade to these updated packages, which contain backported patches to correct these issues.

ID	Name	Product	Family	Severity
198947	RHEL 4 : pam (Unpatched Vulnerability)	Nessus	Red Hat Local Security Checks	medium
68144	Oracle Linux 6 : pam (ELSA-2010-0891)	Nessus	Oracle Linux Local Security Checks	medium
68132	Oracle Linux 5 : pam (ELSA-2010-0819)	Nessus	Oracle Linux Local Security Checks	medium
59704	GLSA-201206-31 : Linux-PAM: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
55103	Ubuntu 8.04 LTS / 10.04 LTS / 10.10 / 11.04 : pam regression (USN-1140-2)	Nessus	Ubuntu Local Security Checks	medium
55102	Ubuntu 8.04 LTS / 10.04 LTS / 10.10 / 11.04 : pam vulnerabilities (USN-1140-1)	Nessus	Ubuntu Local Security Checks	medium
50804	CentOS 5 : pam (CESA-2010:0819)	Nessus	CentOS Local Security Checks	medium
50644	RHEL 6 : pam (RHSA-2010:0891)	Nessus	Red Hat Local Security Checks	high
50447	RHEL 5 : pam (RHSA-2010:0819)	Nessus	Red Hat Local Security Checks	medium

Detections

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CVE-2010-4707

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