content/info/security_bulletin_20020620.txt - httpd-site - Git at Google

 -----BEGIN PGP SIGNED MESSAGE-----


 SUPERSEDES: http://httpd.apache.org/info/security_bulletin_20020617.txt

 Date: June 20, 2002
 Product: Apache Web Server
 Versions: Apache 1.3 all versions including 1.3.24; Apache 2.0 all versions
 up to 2.0.36; Apache 1.2 all versions.

 CVE-2002-0392 (mitre.org) [CERT VU#944335]

 - ----------------------------------------------------------
          ------------UPDATED ADVISORY------------
 - ----------------------------------------------------------
 Introduction:

 While testing for Oracle vulnerabilities, Mark Litchfield discovered a
 denial of service attack for Apache on Windows.  Investigation by the
 Apache Software Foundation showed that this issue has a wider scope, which
 on some platforms results in a denial of service vulnerability, while on
 some other platforms presents a potential remote exploit vulnerability.

 This follow-up to our earlier advisory is to warn of known-exploitable
 conditions related to this vulnerability on both 64-bit platforms and
 32-bit platforms alike.  Though we previously reported that 32-bit
 platforms were not remotely exploitable, it has since been proven by
 Gobbles that certain conditions allowing exploitation do exist.

 Successful exploitation of this vulnerability can lead to the execution of
 arbitrary code on the server with the permissions of the web server child
 process.  This can facilitate the further exploitation of vulnerabilities
 unrelated to Apache on the local system, potentially allowing the intruder
 root access.

 Note that early patches for this issue released by ISS and others do not
 address its full scope.

 Due to the existence of exploits circulating in the wild for some platforms,
 the risk is considered high.

 The Apache Software Foundation has released versions 1.3.26 and 2.0.39
 that address and fix this issue, and all users are urged to upgrade
 immediately.

 As a reminder, we respectfully request that anyone who finds a potential
 vulnerability in our software reports it to security@apache.org.


 - ----------------------------------------------------------
 Full Description:

 Versions of the Apache web server up to and including 1.3.24 and 2.0
 up to and including 2.0.36 contain a bug in the routines that deal with
 requests encoded using chunked encoding.  This bug can be triggered
 remotely, and this functionality is enabled by default.

 In most cases the outcome of the invalid request is that the child process
 dealing with the request will terminate.  At the least, this could help a
 remote attacker launch a denial of service attack as the parent process
 will eventually have to replace the terminated child process, and starting
 new children uses non-trivial amounts of resources.

 On the Windows and Netware platforms, Apache runs one multithreaded child
 process to service requests.  The teardown and subsequent setup time to
 replace the lost child process presents a significant interruption of
 service.  As the Windows and Netware ports create a new process and reread
 the configuration, rather than fork a child process, this delay is much
 more pronounced than on other platforms.

 In Apache 2.0, the error condition is correctly detected, so it will not
 allow an attacker to execute arbitrary code on the server.  However,
 platforms could be using a multithreaded model with multiple concurrent
 requests per child process (although the default preference remains
 multiple processes with a single thread and request per process, and most
 multithreaded models continue to create multiple child processes).  Using
 any multithreaded model, all concurrent requests currently served by the
 affected child process will be lost.

 In Apache 1.3, the issue should cause a stack overflow.  Due to the nature
 of the overflow on 32-bit Unix platforms, this should cause a segmentation
 violation and cause the child to terminate.  However, some 32-bit platforms
 are indeed exploitable due to quirks in their implementation.  64-bit
 platforms are also likely to be exploitable due to a data type conversion
 that occurs within Apache.  We have been made aware that Apache 1.3 on
 Windows is exploitable in a similar way as well.


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	SUPERSEDES: http://httpd.apache.org/info/security_bulletin_20020617.txt

	Date: June 20, 2002
	Product: Apache Web Server
	Versions: Apache 1.3 all versions including 1.3.24; Apache 2.0 all versions
	up to 2.0.36; Apache 1.2 all versions.

	CVE-2002-0392 (mitre.org) [CERT VU#944335]

	- ----------------------------------------------------------
	------------UPDATED ADVISORY------------
	- ----------------------------------------------------------
	Introduction:

	While testing for Oracle vulnerabilities, Mark Litchfield discovered a
	denial of service attack for Apache on Windows. Investigation by the
	Apache Software Foundation showed that this issue has a wider scope, which
	on some platforms results in a denial of service vulnerability, while on
	some other platforms presents a potential remote exploit vulnerability.

	This follow-up to our earlier advisory is to warn of known-exploitable
	conditions related to this vulnerability on both 64-bit platforms and
	32-bit platforms alike. Though we previously reported that 32-bit
	platforms were not remotely exploitable, it has since been proven by
	Gobbles that certain conditions allowing exploitation do exist.

	Successful exploitation of this vulnerability can lead to the execution of
	arbitrary code on the server with the permissions of the web server child
	process. This can facilitate the further exploitation of vulnerabilities
	unrelated to Apache on the local system, potentially allowing the intruder
	root access.

	Note that early patches for this issue released by ISS and others do not
	address its full scope.

	Due to the existence of exploits circulating in the wild for some platforms,
	the risk is considered high.

	The Apache Software Foundation has released versions 1.3.26 and 2.0.39
	that address and fix this issue, and all users are urged to upgrade
	immediately.

	As a reminder, we respectfully request that anyone who finds a potential
	vulnerability in our software reports it to security@apache.org.


	- ----------------------------------------------------------
	Full Description:

	Versions of the Apache web server up to and including 1.3.24 and 2.0
	up to and including 2.0.36 contain a bug in the routines that deal with
	requests encoded using chunked encoding. This bug can be triggered
	remotely, and this functionality is enabled by default.

	In most cases the outcome of the invalid request is that the child process
	dealing with the request will terminate. At the least, this could help a
	remote attacker launch a denial of service attack as the parent process
	will eventually have to replace the terminated child process, and starting
	new children uses non-trivial amounts of resources.

	On the Windows and Netware platforms, Apache runs one multithreaded child
	process to service requests. The teardown and subsequent setup time to
	replace the lost child process presents a significant interruption of
	service. As the Windows and Netware ports create a new process and reread
	the configuration, rather than fork a child process, this delay is much
	more pronounced than on other platforms.

	In Apache 2.0, the error condition is correctly detected, so it will not
	allow an attacker to execute arbitrary code on the server. However,
	platforms could be using a multithreaded model with multiple concurrent
	requests per child process (although the default preference remains
	multiple processes with a single thread and request per process, and most
	multithreaded models continue to create multiple child processes). Using
	any multithreaded model, all concurrent requests currently served by the
	affected child process will be lost.

	In Apache 1.3, the issue should cause a stack overflow. Due to the nature
	of the overflow on 32-bit Unix platforms, this should cause a segmentation
	violation and cause the child to terminate. However, some 32-bit platforms
	are indeed exploitable due to quirks in their implementation. 64-bit
	platforms are also likely to be exploitable due to a data type conversion
	that occurs within Apache. We have been made aware that Apache 1.3 on
	Windows is exploitable in a similar way as well.


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