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Category:   Application (Web Server/CGI)  >   Apache HTTPD Vendors:   Apache Software Foundation
(Conectiva Issues Fix) Apache Web Server Socket Starvation Flaw May Let Remote Users Deny Service
SecurityTracker Alert ID:  1009774
SecurityTracker URL:
CVE Reference:   CVE-2004-0174   (Links to External Site)
Date:  Apr 14 2004
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 2.0.48 and prior versions; 1.3.29 and prior versions
Description:   A vulnerability was reported in the Apache web server. A remote user may be able to cause denial of service conditions.

It is reported that a remote user can establish a short-lived connection to a rarely-accessed listening socket on the target server. This may cause the Apache child process to block new connections until another connection arrives on the rarely-accessed listening socket.

The report indicates that some versions of AIX, Solaris, and Tru64 UNIX are affected, but that FreeBSD and Linux systems are not affected.

Impact:   A remote user may be able to cause the target server to deny connection requests.
Solution:   Conectiva has released a fix.

[Editor's note: The original vulnerability report indicated that this flaw does not affect Linux. However, this Conectiva update includes a fix for the flaw.]

Vendor URL: (Links to External Site)
Cause:   Resource error
Underlying OS:  Linux (Conectiva)
Underlying OS Comments:  Reportedly does not affect FreeBSD or Linux, but this Conectiva patch includes the fix anyway; Conectiva 8, 9

Message History:   This archive entry is a follow-up to the message listed below.
Mar 19 2004 Apache Web Server Socket Starvation Flaw May Let Remote Users Deny Service

 Source Message Contents

Subject:  [conectiva-updates] [CLA-2004:839] Conectiva Security Announcement - apache

Hash: SHA1

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PACKAGE   : apache
SUMMARY   : DoS in mod_ssl and log escape sequences vulnerability
DATE      : 2004-04-13 16:52:00
ID        : CLA-2004:839
RELEASES  : 8, 9

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 Apache[1] is the most popular webserver in use today.
 The Apache team disclosed two vulnerabilities[2] in the Apache Web
 Server that affect Conectiva Linux. Both are fixed in this update:
 CAN-2003-0020: Unescaped characters in error logs[3]: Apache is not
 filtering escape sequences passed by clients as URLs before writing
 its error logs. An attacker can exploit this vulnerability to, for
 example, pass terminal escape sequences to the logs that when viewed
 in vulnerable terminals[4] may trigger the execution of arbitrary
 commands. This vulnerability has been fixed in Apache 2.0.49 and a
 backported patch is included in this update.
 CAN-2004-0113: Denial of Service in mod_ssl[5]: A memory leak has
 been discovered in mod_ssl that may be triggered by sending normal
 HTTP requests to the Apache HTTPS port. An attacker can exploit this
 vulnerability to consume all memory available in the server, thus
 causing a denial of service condition. This problem has been fixed in
 Apache 2.0.49 and a backported patch is included in this update. This
 issue does not affect Conectiva Linux 8 (which has Apache 1.3.X).
 Additionally, this update includes a fix for a denial of service
 issue[6] which is reported to not affect Apache on Linux systems.

 It is recommended that all Apache users upgrade their packages.
 IMPORTANT: it is necessary to manually restart the httpd server after
 upgrading the packages. In order to do this, execute the following as
 # service httpd stop
 (wait a few seconds and check with "pidof httpd" if there are any
 httpd processes running. On a busy webserver this could take a little
 # service httpd start


 The apt tool can be used to perform RPM packages upgrades:

 - run:                 apt-get update
 - after that, execute: apt-get upgrade

 Detailed instructions regarding the use of apt and upgrade examples 
 can be found at

- -------------------------------------------------------------------------
All packages are signed with Conectiva's GPG key. The key and instructions
on how to import it can be found at
Instructions on how to check the signatures of the RPM packages can be
found at

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All our advisories and generic update instructions can be viewed at

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Copyright (c) 2004 Conectiva Inc.

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Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see



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