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Title:       EGI SVG 'ADVISORY' **UPDATE** [TLP:WHITE] HIGH risk - Squid Vulnerability  [EGI-SVG-2021-17247]

Date:        2021-05-12
Updated:     2021-06-03

Update 2021-06-03

EGI UMD 4 has been updated with frontier-squid-4.15-1.2 that fixes the vulnerability.

Affected software and risk

HIGH risk vulnerability concerning Squid

Package : Squid, including Frontier Squid [R 3] before version 4.15

The Squid project has publicly announced [R 1] new vulnerabilities, one of which is deemed HIGH risk, viz. CVE-2020-25097 [R 2], because it may allow services to be exposed that are not directly accessible from the client host. The other ones only concern potential denial of service and hence are deemed low risk.

Actions required/recommended

Sites are recommended to update relevant components or apply the mitigation detailed below as soon as possible.

Component installation information

The official repository for the distribution of grid middleware for EGI sites is which contains the EGI Unified Middleware Distribution (UMD).
Sites using frontier-squid from the EGI UMD 4 should see:

The fixed version is frontier-squid-4.15-1.2.

Sites installing Squid from anywhere else should see information from their provider.

Fixed versions (squid-3.5.20-17.el7_9.6) are available for RHEL 7 [R 5], CentOS 7 [R 6], SL 7 [R 7].


For sites that cannot upgrade in a timely manner, temporary workarounds for the
high-risk vulnerability are provided here.

If frontier-squid is used, update with the following line and either reload or restart frontier-squid:

    setoption("uri_whitespace", "deny")

If a plain squid is used instead, set the "uri_whitespace" directive in squid.conf to either:

    uri_whitespace deny


    uri_whitespace encode

and restart the squid service.

Affected software details

All versions of squid and frontier-squid earlier than 4.15 are affected. 

Additional information

Note that exposure of squid services should usually be limited by access control to addresses within a local area network.


** WHITE information - Unlimited distribution 
   - see for distribution restrictions***    


Minor updates may be made without re-distribution to the sites


Comments or questions should be sent to svg-rat  at

If you find or become aware of another vulnerability which is relevant to EGI you may report it by e-mail to  

report-vulnerability at
the EGI Software Vulnerability Group will take a look according to the procedure defined in [R 4]  

Note that this is undergoing revision to fully handle vulnerabilities in the EOSC-hub era. 


[R 1]

[R 2]

[R 3]

[R 4]

[R 5]

[R 6]

[R 7]


SVG was alerted to this vulnerability by Dave Dykstra.

Information on these vulnerabilities contained in this advisory is based on the corresponding OSG advisory for these vulnerabilities.

Yyyy-mm-dd  [EGI-SVG-2021-17247] 

2021-05-10 SVG alerted to this issue by Dave Dykstra (FNAL)
2021-05-10 Acknowledgement from the EGI SVG to the reporter
2021-05-10 Investigation of vulnerability and relevance to EGI carried out 
2021-05-11 EGI SVG Risk Assessment completed 
2021-05-11 SVG drafts advisory based on OSG announcement
2021-05-12 Advisory sent to sites
2021-06-03 Update sent to sites


This advisory has been prepared as part of the effort to fulfil EGI SVG's purpose 
"To minimize the risk to the EGI infrastructure arising from software vulnerabilities"

The risk is that assessed by the group, according to the EGI SVG issue handling procedure [R 4]  in the context of how the software is used in the EGI infrastructure. It is the opinion of the group, we do not guarantee it to be correct. The risk may also be higher or lower in other deployments depending on how the software is used.   

This advisory is subject to the Creative commons license and the EGI Software Vulnerability Group must be credited. 

Note that the SVG issue handling procedure is currently under review, to take account of the increasing inhomogeneity of the EGI infrastructure and the services in the EOSC-hub catalogue.

On behalf of the EGI SVG,