Bug 1923636 (CVE-2021-20239) - CVE-2021-20239 kernel: setsockopt System Call Untrusted Pointer Dereference Information Disclosure
Summary: CVE-2021-20239 kernel: setsockopt System Call Untrusted Pointer Dereference I...
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2021-20239
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact: Zhiqian Guan
URL:
Whiteboard:
Depends On: 1933655 1923640 1929475 1929476
Blocks: 1923644
TreeView+ depends on / blocked
 
Reported: 2021-02-01 17:21 UTC by Pedro Sampaio
Modified: 2021-11-09 18:23 UTC (History)
53 users (show)

Fixed In Version: kernel 5.4.92
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the BPF protocol. This flaw allows an attacker with a local account to leak information about kernel internal addresses. The highest threat from this vulnerability is to confidentiality.
Clone Of:
Environment:
Last Closed: 2021-11-08 01:29:46 UTC
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2021:4140 0 None None None 2021-11-09 17:21:41 UTC
Red Hat Product Errata RHSA-2021:4356 0 None None None 2021-11-09 18:23:46 UTC

Description Pedro Sampaio 2021-02-01 17:21:42 UTC 
A flaw was found in the Linux kernels implementation of BPF. A local user with CAP_NET_ADMIN can attach an ebpf filter to setsockopt() syscall.   This filter can be triggered under the right conditions to leak kernel internal information.  This could allow an attacker to determine the layout of information in kernel memory to be used in future attacks.

This flaw  is also known as ZDI-21-100.

References:

https://www.zerodayinitiative.com/advisories/ZDI-21-100/
https://gist.github.com/Ga-ryo/2ec958e78f55c5d18558960f3fe1c6ec
Comment 1 Pedro Sampaio 2021-02-01 17:22:31 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1923640]
Comment 2 Justin M. Forbes 2021-02-02 16:00:03 UTC 
This was fixed for Fedora with the 5.10.10 stable kernel updates.
Comment 4 Wade Mealing 2021-02-12 07:05:12 UTC 
This flaw is rated as low, it is an information leak which may 'aid' an attacker to privesc, but not privesc itself
Comment 10 Wade Mealing 2021-02-17 02:13:06 UTC 
Mitigation:

Loading a filter is a privileged (CAP_SYS_ADMIN or root) operation. Once any filter is used, this attack is capable of being used by an unprivileged user.  There is no known mitigation that product security finds suitable for this flaw.
Comment 29 errata-xmlrpc 2021-11-09 17:21:38 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:4140 https://access.redhat.com/errata/RHSA-2021:4140
Comment 30 errata-xmlrpc 2021-11-09 18:23:44 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:4356 https://access.redhat.com/errata/RHSA-2021:4356
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