Bug 2004949 (CVE-2021-3773) - CVE-2021-3773 kernel: lack of port sanity checking in natd and netfilter leads to exploit of OpenVPN clients [NEEDINFO]
Summary: CVE-2021-3773 kernel: lack of port sanity checking in natd and netfilter lead...
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2021-3773
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2006005 Red Hat2006167 Red Hat2006168 Red Hat2006169
Blocks: Red Hat2001550 Embargoed2004199
TreeView+ depends on / blocked
 
Reported: 2021-09-16 13:37 UTC by Guilherme de Almeida Suckevicz
Modified: 2023-05-26 08:30 UTC (History)
48 users (show)

Fixed In Version: kernel 5.14.0-49.el9, kernel 5.15.15-100.fc34, kernel 5.15.15-200.fc35
Doc Type: If docs needed, set a value
Doc Text:
A flaw in netfilter could allow a network-connected attacker to infer openvpn connection endpoint information for further use in traditional network attacks.
Clone Of:
Environment:
Last Closed: 2022-05-11 10:16:30 UTC
mrehak: needinfo? (rkeshri)

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2022:2229 0 None None None 2022-05-12 11:26:39 UTC
Red Hat Product Errata RHBA-2022:4630 0 None None None 2022-05-18 11:46:24 UTC
Red Hat Product Errata RHBA-2022:4693 0 None None None 2022-05-19 05:10:49 UTC
Red Hat Product Errata RHBA-2022:4969 0 None None None 2022-06-08 18:39:59 UTC
Red Hat Product Errata RHBA-2022:5088 0 None None None 2022-06-16 11:23:12 UTC
Red Hat Product Errata RHSA-2022:1975 0 None None None 2022-05-10 14:39:45 UTC
Red Hat Product Errata RHSA-2022:1988 0 None None None 2022-05-10 14:45:35 UTC

Description Guilherme de Almeida Suckevicz 2021-09-16 13:37:43 UTC 
OpenVPN's use of Netfilter makes it susceptible to several attacks that can cause denial-of-service, deanonymization of clients, or redirection of a victim client connection to an attacker controlled server.

Reference:
https://www.openwall.com/lists/oss-security/2021/09/08/3
https://breakpointingbad.com/2021/09/08/Port-Shadows-via-Network-Alchemy.html
Comment 1 Guilherme de Almeida Suckevicz 2021-09-20 16:35:52 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 2006005]
Comment 7 Wade Mealing 2022-03-04 04:56:07 UTC 
I wont be argueing the rescore, complexit is high, because the argued example is not in most openvpn nat scenarios, and even then you wont get I:H, because you can't modify anything..  Dunno what to say.
Comment 8 errata-xmlrpc 2022-05-10 14:39:42 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2022:1975 https://access.redhat.com/errata/RHSA-2022:1975
Comment 9 errata-xmlrpc 2022-05-10 14:45:31 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2022:1988 https://access.redhat.com/errata/RHSA-2022:1988
Comment 10 Product Security DevOps Team 2022-05-11 10:16:26 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2021-3773
Comment 11 bmixonba 2023-05-15 22:56:37 UTC 
(In reply to Wade Mealing from comment #7)
> I wont be argueing the rescore, complexit is high, because the argued
> example is not in most openvpn nat scenarios, and even then you wont get
> I:H, because you can't modify anything..  Dunno what to say.

Hi Wade, I have two questions I am hoping you can answer. First, what do you think are more common openvpn nat scenarios? Second, what is I:H?
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