It was reported that a race condition exists in libnss-ldap, an NSS module for using LDAP as a naming service, which could cause denial of service attacks if applications use pthreads.

This problem was spotted in the dovecot IMAP/POP server but potentially affects more programs.

An updated nss_ldap package that fixes a security issue and several bugs is now available.

This update has been rated as having low security impact by the Red Hat Security Response Team.

The nss_ldap package contains the nss_ldap and pam_ldap modules. The nss_ldap module is a plug-in which allows applications to retrieve information about users and groups from a directory server. The pam_ldap module allows PAM-aware applications to use a directory server to verify user passwords.

A race condition was discovered in nss_ldap which affected certain applications which make LDAP connections, such as Dovecot. This could cause nss_ldap to answer a request for information about one user with information about a different user. (CVE-2007-5794)

In addition, these updated packages fix the following bugs :

* a build error prevented the nss_ldap module from being able to use DNS to discover the location of a directory server. For example, when the /etc/nsswitch.conf configuration file was configured to use 'ldap', but no 'host' or 'uri' option was configured in the /etc/ldap.conf configuration file, no directory server was contacted, and no results were returned.

* the 'port' option in the /etc/ldap.conf configuration file on client machines was ignored. For example, if a directory server which you were attempting to use was listening on a non-default port (i.e. not ports 389 or 636), it was only possible to use that directory server by including the port number in the 'uri' option. In this updated package, the 'port' option works as expected.

* pam_ldap failed to change an expired password if it had to follow a referral to do so, which could occur, for example, when using a slave directory server in a replicated environment. An error such as the following occurred after entering a new password: 'LDAP password information update failed: Can't contact LDAP server Insufficient 'write' privilege to the 'userPassword' attribute'

This has been resolved in this updated package.

* when the 'pam_password exop_send_old' password-change method was configured in the /etc/ldap.conf configuration file, a logic error in the pam_ldap module caused client machines to attempt to change a user's password twice. First, the pam_ldap module attempted to change the password using the 'exop' request, and then again using an LDAP modify request.

* on Red Hat Enterprise Linux 5.1, rebuilding nss_ldap-253-5.el5 when the krb5-*-1.6.1-17.el5 packages were installed failed due to an error such as the following :

+ /builddir/build/SOURCES/dlopen.sh ./nss_ldap-253/nss_ldap.so dlopen() of '././nss_ldap-253/nss_ldap.so' failed:
./././nss_ldap-253/nss_ldap.so: undefined symbol: request_key error:
Bad exit status from /var/tmp/rpm-tmp.62652 (%build)

The missing libraries have been added, which resolves this issue.

When recursively enumerating the set of members in a given group, the module would allocate insufficient space for storing the set of member names if the group itself contained other groups, thus corrupting the heap. This update includes a backported fix for this bug.

Users of nss_ldap should upgrade to these updated packages, which contain backported patches to correct this issue and fix these bugs.

nss_ldap returned incorrect data under certain circumstances to the calling process. Some applications could therefore work with wrong user data (CVE-2007-5794).

The remote Oracle Linux 5 host has a package installed that is affected by a vulnerability as referenced in the ELSA-2008-0389 advisory.

    [253-12]
    - rebuild

    [253-11]
    - backport changes to group parsing from version 254 to fix heap corruption       when parsing nested groups (#444031)

    [253-10]
    - remove unnecessary nss_ldap linkage to libnsl (part of #427370)

    [253-9]
    - rebuild

    [253-8]
    - incorporate Tomas Janouseks fix to prevent re-use of connections across       fork() (#252337)

    [253-7]
    - add keyutils-libs-devel and libselinux-devel as a buildrequires: in order to       static link with newer Kerberos (#427370)

    [253-6]
    - suppress password-expired errors encountered during referral chases during       modify requests (#335661)
    - interpret server-supplied policy controls when chasing referrals, so that       we dont give up when following a referral for a password change after       reset (#335661)
    - dont attempt to change the password using ldap_modify if the password       change mode is 'exop_send_old' (we already didnt for 'exop') (#364501)
    - dont drop the supplied password if the directory server indicates that       the password needs to be changed because its just been reset: we may need       it to chase a referral later (#335661)
    - correctly detect libresolv and build a URI using discovered settings, so that       server discovery can work again (#254172)
    - honor the 'port' setting again by correctly detecting when a URI doesnt       already specify one (#326351)

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

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

An updated nss_ldap package that fixes a security issue and several bugs is now available.

This update has been rated as having low security impact by the Red Hat Security Response Team.

The nss_ldap package contains the nss_ldap and pam_ldap modules. The nss_ldap module is a plug-in which allows applications to retrieve information about users and groups from a directory server. The pam_ldap module allows PAM-aware applications to use a directory server to verify user passwords.

A race condition was discovered in nss_ldap, which affected certain applications that make LDAP connections, such as Dovecot. This could cause nss_ldap to answer a request for information about one user with the information about a different user. (CVE-2007-5794)

As well, this updated package fixes the following bugs :

* in certain situations, on Itanium(R) architectures, when an application performed an LDAP lookup for a highly populated group, for example, containing more than 150 members, the application crashed, or may have caused a segmentation fault. As well, this issue may have caused commands, such as 'ls', to return a 'ber_free_buf: Assertion' error.

* when an application enumerated members of a netgroup, the nss_ldap module returned a successful status result and the netgroup name, even when the netgroup did not exist. This behavior was not consistent with other modules. In this updated package, nss_ldap no longer returns a successful status when the netgroup does not exist.

* in master and slave server environments, with systems that were configured to use a read-only directory server, if user log in attempts were denied because their passwords had expired, and users attempted to immediately change their passwords, the replication server returned an LDAP referral, instructing the pam_ldap module to resissue its request to a different server; however, the pam_ldap module failed to do so. In these situations, an error such as the following occurred :

LDAP password information update failed: Can't contact LDAP server Insufficient 'write' privilege to the 'userPassword' attribute of entry [entry]

In this updated package, password changes are allowed when binding against a slave server, which resolves this issue.

* when a system used a directory server for naming information, and 'nss_initgroups_ignoreusers root' was configured in '/etc/ldap.conf', dbus-daemon-1 would hang. Running the 'service messagebus start' command did not start the service, and it did not fail, which would stop the boot process if it was not cancelled.

As well, this updated package upgrades nss_ldap to the version as shipped with Red Hat Enterprise Linux 5.

Users of nss_ldap are advised to upgrade to this updated package, which resolves these issues.

A race condition in nss_ldap, when used in applications that use pthread and fork after a call to nss_ldap, does not properly handle the LDAP connection, which might cause nss_ldap to return the wrong user data to the wrong process, giving one user access to data belonging to another user, in some cases.

The updated package hais been patched to prevent this issue.

A race condition was discovered in nss_ldap which affected certain applications which make LDAP connections, such as Dovecot. This could cause nss_ldap to answer a request for information about one user with information about a different user. (CVE-2007-5794)

In addition, these updated packages fix the following bugs :

  - a build error prevented the nss_ldap module from being     able to use DNS to discover the location of a directory     server. For example, when the /etc/nsswitch.conf     configuration file was configured to use 'ldap', but no     'host' or 'uri' option was configured in the     /etc/ldap.conf configuration file, no directory server     was contacted, and no results were returned.

  - the 'port' option in the /etc/ldap.conf configuration     file on client machines was ignored. For example, if a     directory server which you were attempting to use was     listening on a non-default port (i.e. not ports 389 or     636), it was only possible to use that directory server     by including the port number in the 'uri' option. In     this updated package, the 'port' option works as     expected.

  - pam_ldap failed to change an expired password if it had     to follow a referral to do so, which could occur, for     example, when using a slave directory server in a     replicated environment. An error such as the following     occurred after entering a new password: 'LDAP password     information update failed: Can't contact LDAP server     Insufficient 'write' privilege to the 'userPassword'     attribute'

This has been resolved in this updated package.

  - when the 'pam_password exop_send_old' password-change     method was configured in the /etc/ldap.conf     configuration file, a logic error in the pam_ldap module     caused client machines to attempt to change a user's     password twice. First, the pam_ldap module attempted to     change the password using the 'exop' request, and then     again using an LDAP modify request.

  - on Red Hat Enterprise Linux 5.1, rebuilding     nss_ldap-253-5.el5 when the krb5-*-1.6.1-17.el5 packages     were installed failed due to an error such as the     following :

  - /builddir/build/SOURCES/dlopen.sh     ./nss_ldap-253/nss_ldap.so dlopen() of     '././nss_ldap-253/nss_ldap.so' failed:
    ./././nss_ldap-253/nss_ldap.so: undefined symbol:
    request_key error: Bad exit status from     /var/tmp/rpm-tmp.62652 (%build)

The missing libraries have been added, which resolves this issue.

When recursively enumerating the set of members in a given group, the module would allocate insufficient space for storing the set of member names if the group itself contained other groups, thus corrupting the heap. This update includes a backported fix for this bug.

A race condition was discovered in nss_ldap, which affected certain applications that make LDAP connections, such as Dovecot. This could cause nss_ldap to answer a request for information about one user with the information about a different user. (CVE-2007-5794)

As well, this updated package fixes the following bugs :

  - in certain situations, on Itanium(R) architectures, when     an application performed an LDAP lookup for a highly     populated group, for example, containing more than 150     members, the application crashed, or may have caused a     segmentation fault. As well, this issue may have caused     commands, such as 'ls', to return a 'ber_free_buf:
    Assertion' error.

  - when an application enumerated members of a netgroup,     the nss_ldap module returned a successful status result     and the netgroup name, even when the netgroup did not     exist. This behavior was not consistent with other     modules. In this updated package, nss_ldap no longer     returns a successful status when the netgroup does not     exist.

  - in master and slave server environments, with systems     that were configured to use a read-only directory     server, if user log in attempts were denied because     their passwords had expired, and users attempted to     immediately change their passwords, the replication     server returned an LDAP referral, instructing the     pam_ldap module to resissue its request to a different     server; however, the pam_ldap module failed to do so. In     these situations, an error such as the following     occurred :

LDAP password information update failed: Can't contact LDAP server Insufficient 'write' privilege to the 'userPassword' attribute of entry [entry]

In this updated package, password changes are allowed when binding against a slave server, which resolves this issue.

  - when a system used a directory server for naming     information, and 'nss_initgroups_ignoreusers root' was     configured in '/etc/ldap.conf', dbus-daemon-1 would     hang. Running the 'service messagebus start' command did     not start the service, and it did not fail, which would     stop the boot process if it was not cancelled.

As well, this updated package upgrades nss_ldap to the version as shipped with Scientific Linux 5.

The remote host is affected by the vulnerability described in GLSA-200711-33 (nss_ldap: Information disclosure)

    Josh Burley reported that nss_ldap does not properly handle the LDAP     connections due to a race condition that can be triggered by     multi-threaded applications using nss_ldap, which might lead to     requested data being returned to a wrong process.
  Impact :

    Remote attackers could exploit this race condition by sending queries     to a vulnerable server using nss_ldap, possibly leading to theft of     user credentials or information disclosure (e.g. Dovecot returning     wrong mailbox contents).
  Workaround :

    There is no known workaround at this time.

nss_ldap returned incorrect data under certain circumstances to the calling process. Some applications could therefore work with wrong user data. (CVE-2007-5794)

ID	Name	Product	Family	Published	Updated	Severity
29338	Debian DSA-1430-1 : libnss-ldap - denial of service	Nessus	Debian Local Security Checks	12/12/2007	1/4/2021	medium
32426	RHEL 5 : nss_ldap (RHSA-2008:0389)	Nessus	Red Hat Local Security Checks	5/22/2008	1/14/2021	medium
30196	openSUSE 10 Security Update : nss_ldap (nss_ldap-4773)	Nessus	SuSE Local Security Checks	2/6/2008	1/14/2021	medium
180599	Oracle Linux 5 : nss_ldap (ELSA-2008-0389)	Nessus	Oracle Linux Local Security Checks	9/7/2023	10/23/2024	critical
33583	RHEL 4 : nss_ldap (RHSA-2008:0715)	Nessus	Red Hat Local Security Checks	7/25/2008	1/14/2021	medium
37403	Mandriva Linux Security Advisory : nss_ldap (MDVSA-2008:049)	Nessus	Mandriva Local Security Checks	4/23/2009	1/6/2021	medium
60407	Scientific Linux Security Update : nss_ldap on SL5.x i386/x86_64	Nessus	Scientific Linux Local Security Checks	8/1/2012	1/14/2021	medium
60452	Scientific Linux Security Update : nss_ldap on SL4.x i386/x86_64	Nessus	Scientific Linux Local Security Checks	8/1/2012	1/14/2021	medium
28322	GLSA-200711-33 : nss_ldap: Information disclosure	Nessus	Gentoo Local Security Checks	11/26/2007	1/6/2021	medium
30197	SuSE 10 Security Update : nss_ldap (ZYPP Patch Number 4781)	Nessus	SuSE Local Security Checks	2/6/2008	1/14/2021	medium

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