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Category:   Application (Generic)  >   Squid Vendors:
(SCO Issues Fix) Squid Proxy Cache '%00' URL Character Access Control Bug May Let Remote Users Bypass Certain Access Controls
SecurityTracker Alert ID:  1011128
SecurityTracker URL:
CVE Reference:   CVE-2004-0189   (Links to External Site)
Date:  Sep 1 2004
Impact:   Host/resource access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): Squid-2.x up to and including 2.5.STABLE4
Description:   A vulnerability was reported in the Squid Proxy Cache server in the processing of URLs containing '%00'. A remote user may be able to bypass certain access controls.

It is reported that a flaw in the '%xx' URL decoding function may allow a remote user to bypass access controls that use 'url_regex' access control list (ACL) types. The report indicates that Squid will insert a NUL character in place of '%00' in a URL before analyzing the URL for access control purposes. As a result, the '' URL will not be properly detected as a URL to be denied in accordance with the following type of access control configuration:

acl BadSite url_regex www\.example\.com
http_access deny BadSite

In this example, Squid will attempt to compare 'http://foo' with 'www\.example\.com' and will not find a match, so the URL will not be denied.

Mitch Adair is credited with reporting this flaw.

Impact:   A remote user may be able to submit a specially crafted URL to bypass url_regex access controls.
Solution:   SCO has issued a fix, described at:

Vendor URL: (Links to External Site)
Cause:   Access control error
Underlying OS:  Linux (Caldera/SCO)
Underlying OS Comments:  OpenServer 5.0.6, 5.0.7

Message History:   This archive entry is a follow-up to the message listed below.
Mar 1 2004 Squid Proxy Cache '%00' URL Character Access Control Bug May Let Remote Users Bypass Certain Access Controls

 Source Message Contents

Subject:  OpenServer 5.0.6 OpenServer 5.0.7 : squid %-encoded characters in a URL

Hash: SHA1


			SCO Security Advisory

Subject:		OpenServer 5.0.6 OpenServer 5.0.7 : squid %-encoded characters in a URL
Advisory number: 	SCOSA-2004.13
Issue date: 		2004 August 31
Cross reference:	sr890342 fz529456 erg712609 CAN-2004-0189

1. Problem Description

	The "%xx" URL decoding function in Squid 2.5STABLE4 and
	earlier allows remote attackers to bypass url_regex ACLs
	via a URL with a NULL ("%00") character, which causes Squid
	to use only a portion of the requested URL when comparing
	it against the access control lists. 

	The Common Vulnerabilities and Exposures project ( 
	has assigned the name CAN-2004-0189 to this issue.

2. Vulnerable Supported Versions

	System				Binaries
	OpenServer 5.0.6 		Squid distribution < 2.5.STABLE5
	OpenServer 5.0.7 		Squid distribution < 2.5.STABLE5

3. Solution

	The proper solution is to install the latest packages.

4. OpenServer 5.0.6

	4.1 First install oss646c or later

        4.2 Location of oss646c

        4.3 Verification of oss646c

        MD5 (VOL.000.000) = f19b6c6949f615316bfb075d249989e8
        MD5 (VOL.000.001) = 341ff8553aecd2c7b0c2beaf83030d0f
        MD5 (VOL.000.002) = 6e46708ad8029e12280d4f9ac60ab814
        MD5 (VOL.000.003) = 2868b64a6a6db742adb3b485be645d7e
        MD5 (VOL.000.004) = 1696fe1db9bb063827ee5e76e58dff84
        MD5 (VOL.000.005) = f39da342f8af72fcaccdf478dca04109
        MD5 (VOL.000.006) = 2b31611c8af7d2e7910d6e8e3cf701a6
        MD5 (VOL.000.007) = d0175c0f4e3ed29435b1eab95609f8f4
        MD5 (VOL.000.008) = aa9e8a525c341fed077f981b1dacb486
        MD5 (VOL.000.009) = 8e023af67b57507824406bdda322079a
        MD5 (VOL.000.010) = 2b46e8adba8ae0b64109f2069da978a2

	4.4 Installation of oss646c


	4.5 Next install xorg-6.7.0Ba or later

	4.6 Location of xorg-6.7.0Ba

	4.7 Verification of xorg-6.7.0Ba

	MD5 (VOL.000.000) = 289d1070c4135e4d25a20501dbca08d8
	MD5 (VOL.000.001) = 4111dadf961d4ef88e89112070f3e811
	MD5 (VOL.000.002) = 4c4cdf4bf4c28045b7b323cfa407829f
	MD5 (VOL.000.003) = d7e8da318d1c4df6fff14f60d993cf45
	MD5 (VOL.000.004) = bfc0571f1fededd1780fafa76db9be90

	4.8 Installation of xorg-6.7.0Ba


	4.9 Next install gwxlibs-1.3.3Db or later

	4.10 Location of gwxlibs-1.3.3Db

        4.11 Verification

        MD5 (VOL.000.000) = a85cf35c417903522392064aaa98f0a4
        MD5 (VOL.000.001) = d4383d6bc74bb6e873e7a4c8dfdc4e6b
        MD5 (VOL.000.002) = c5657b1358ef96177ae15fdcfec7132f
        MD5 (VOL.000.003) = 4c88ceb3502330b4c4d5e07ca7fc5214

	4.12 Installation of gwxlibs-1.3.3Db


	4.13 Next install perl-5.8.4Aa or later

	4.14 Location of perl-5.8.4Aa

	4.15 Verification

	MD5 (VOL.000.000) = b83b5e0ae513a1cb206baf37c4741653
	MD5 (VOL.000.001) = 1ab35276079e7661e38b72047cec488a
	MD5 (VOL.000.002) = 64a76371eae54e95d0b7e99be25f0a8a
	MD5 (VOL.000.003) = 724521beddc740ae4958fd63d1c45f3f
	MD5 (VOL.000.004) = f1d631477f16ce7b9512fbe60d9e3d0e

	4.16 Installation of perl-5.8.4Aa


	4.17 Location of Squid Fixed Binaries

	4.18 Verification

	MD5 (VOL.000.000) = 656d0097b861d9e2375f672579e15c6b
	MD5 (VOL.000.001) = 4f15cb68083fb6ceff3dd3c72aed41a2
	MD5 (VOL.000.002) = 6fbf1b23e9d86f621de916bca4e476b3
	MD5 (VOL.000.003) = fefcfc2f2d4f56e8be34d917a882bd41

	md5 is available for download from

	4.19 Installing Fixed Binaries

	Upgrade the affected binaries with the following sequence:

	1) Download the VOL* files to a directory.

	2) Run the custom command, specify an install from media
	images, and specify the directory as the location of
	the images.

5. OpenServer 5.0.7

	5.1 Location of Fixed Binaries

	Supplement CD 3

	5.2 Verification

	MD5 (osr507suppcd3.iso) = 129229594bd3a020db429e7de8b95def

	md5 is available for download from

	5.3 Installing Fixed Binaries

	See the Supplement CD 3 Release Notes

6. References

	Specific references for this advisory:

	SCO security resources:

	SCO security advisories via email

	This security fix closes SCO incidents sr890342 fz529456

7. Disclaimer

	SCO is not responsible for the misuse of any of the information
	we provide on this website and/or through our security
	advisories. Our advisories are a service to our customers
	intended to promote secure installation and use of SCO


Version: GnuPG v1.2.4 (SCO/UNIX_SVR5)



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