Bug 1959397 (CVE-2020-13529) - CVE-2020-13529 systemd: DHCP FORCERENEW authentication not implemented can cause a system running the DHCP client to have its network reconfigured
Summary: CVE-2020-13529 systemd: DHCP FORCERENEW authentication not implemented can ca...
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2020-13529
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
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Whiteboard:
Depends On: 1962041 1959398 1961234 1961238 1961239 1961240 1961241 1961251 1962040 1966123
Blocks: 1959399
TreeView+ depends on / blocked
 
Reported: 2021-05-11 13:09 UTC by Guilherme de Almeida Suckevicz
Modified: 2022-04-17 21:23 UTC (History)
27 users (show)

Fixed In Version:
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Doc Text:
An exploitable denial of service vulnerability exists in systemd which does not fully implement RFC3203, as it does not support authentication of FORCERENEW packets. A specially crafted DHCP FORCERENEW packet can cause a system, running the DHCP client, to be vulnerable to a DHCP ACK spoofing attack. An attacker can forge a pair of FORCERENEW and DCHPACK packets to reconfigure the system with arbitrary network settings.
Clone Of:
Environment:
Last Closed: 2021-11-09 22:21:33 UTC

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System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2021:4361 0 None None None 2021-11-09 18:28:30 UTC

Description Guilherme de Almeida Suckevicz 2021-05-11 13:09:58 UTC 
An exploitable denial-of-service vulnerability exists in Systemd 245. A specially crafted DHCP FORCERENEW packet can cause a server running the DHCP client to be vulnerable to a DHCP ACK spoofing attack. An attacker can forge a pair of FORCERENEW and DCHP ACK packets to reconfigure the server.

References:
https://talosintelligence.com/vulnerability_reports/TALOS-2020-1142
https://github.com/systemd/systemd/issues/16774
Comment 1 Guilherme de Almeida Suckevicz 2021-05-11 13:10:37 UTC 
Created systemd tracking bugs for this issue:

Affects: fedora-all [bug 1959398]
Comment 2 Riccardo Schirone 2021-05-17 14:43:15 UTC 
DHCP reconfigure extension RFC: https://datatracker.ietf.org/doc/html/rfc3203
Comment 3 Riccardo Schirone 2021-05-17 14:43:57 UTC 
Authentication for DHCP Messages RFC: https://datatracker.ietf.org/doc/html/rfc3118
Comment 8 Riccardo Schirone 2021-05-17 16:06:19 UTC 
systemd in upstream version v216 introduced partial support for DHCP FORCERENEW (RFC 3203) with [1]. However authentication of FORCERENEW packets is not implemented, thus it is possible for an adjacent attacker on the local network to forge such packets and trick a system into re-accepting DHCPACK packets, which include all the network settings.

[1] https://github.com/systemd/systemd/commit/615c1467c81411bf1d19fd7092e8995b5ebadc13
Comment 9 Riccardo Schirone 2021-05-17 16:08:50 UTC 
There is no available fix at this time for this issue, as upstream is considering this issue as a RFE rather than a vulnerability [2].

[2] https://bugzilla.redhat.com/show_bug.cgi?id=1959398#c2
Comment 12 Riccardo Schirone 2021-06-24 09:06:08 UTC 
Temporary fix upstream, at least until RFC6704 (Forcerenew Nonce Authentication) is implemented:
https://github.com/systemd/systemd/commit/6222acc2b59309ac6187450d9e65eceb1b7cc1c5
Comment 14 errata-xmlrpc 2021-11-09 18:28:27 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:4361 https://access.redhat.com/errata/RHSA-2021:4361
Comment 15 Product Security DevOps Team 2021-11-09 22:21:30 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-2020-13529
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