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Squid Proxy Cache Security Update Advisory SQUID-2020:9
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Advisory ID: | SQUID-2020:9
Date: | August 23, 2020
Summary: | Denial of Service
| processing Cache Digest Response
Affected versions: | Squid 3.x -> 3.5.28
| Squid 4.x -> 4.12
| Squid 5.x -> 5.0.3
Fixed in version: | Squid 4.13 and 5.0.4
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CVE Assignment pending
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Problem Description:
Due to Improper Input Validation Squid is vulnerable to a Denial
of Service attack against the machine operating Squid.
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Severity:
This problem allows a trusted peer to deliver to perform Denial
of Service by consuming all available CPU cycles on the machine
running Squid when handling a crafted Cache Digest response
message.
This attack is limited to Squid using cache_peer with cache
digests feature.
CVSS Score of 9.5
<https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:H/RL:O/RC:C/CR:X/IR:X/AR:H/MAV:N/MAC:L/MPR:X/MUI:N/MS:C/MC:N/MI:N/MA:H&version=3.1>
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Updated Packages:
This bug is fixed by Squid versions 4.13 and 5.0.4.
In addition, patches addressing this problem for the stable
releases can be found in our patch archives:
Squid 4:
<http://www.squid-cache.org/Versions/v4/changesets/SQUID-2020_9.patch>
If you are using a prepackaged version of Squid then please refer
to the package vendor for availability information on updated
packages.
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Determining if your version is vulnerable:
All Squid built using --disable-cache-digests are not vulnerable.
All Squid without cache_peer directives configured are not
vulnerable.
All Squid-3.x up to and including 3.5.28 using cache_peer
directives with no-digest option configured are not vulnerable.
All Squid-3.x up to and including 3.5.28 using cache_peer
directives without the no-digest option configured are
vulnerable.
All Squid-4.x up to and including 4.12 using cache_peer
directives with no-digest option configured are not vulnerable.
All Squid-4.x up to and including 4.12 using cache_peer
directives without the no-digest option configured are
vulnerable.
All Squid-5.x up to and including 5.0.3 using cache_peer
directives with no-digest option configured are not vulnerable.
All Squid-5.x up to and including 5.0.3 using cache_peer
directives without the no-digest option configured are
vulnerable.
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Workaround:
Either,
Add the no-digest option to all cache_peer lines in squid.conf
Or,
Build Squid with --disable-cache-digests
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Contact details for the Squid project:
For installation / upgrade support on binary packaged versions
of Squid: Your first point of contact should be your binary
package vendor.
If you install and build Squid from the original Squid sources
then the <squid-users@xxxxxxxxxxxxxxxxxxxxx> mailing list is your
primary support point. For subscription details see
<http://www.squid-cache.org/Support/mailing-lists.html>.
For reporting of non-security bugs in the latest STABLE release
the squid bugzilla database should be used
<http://bugs.squid-cache.org/>.
For reporting of security sensitive bugs send an email to the
<squid-bugs@xxxxxxxxxxxxxxxxxxxxx> mailing list. It's a closed
list (though anyone can post) and security related bug reports
are treated in confidence until the impact has been established.
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Credits:
This vulnerability was discovered by Lubos Uhliarik of RedHat.
Fixed by Eduard Bagdasaryan (The Measurement Factory).
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Revision history:
2019-09-30 17:12:18 UTC Initial Report
2020-07-29 20:51:58 UTC Fix committed
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END
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