Bug 2015046 (CVE-2021-3864) - CVE-2021-3864 kernel: descendant's dumpable setting with certain SUID binaries
Summary: CVE-2021-3864 kernel: descendant's dumpable setting with certain SUID binaries
Keywords:
Status: CLOSED NOTABUG
Alias: CVE-2021-3864
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: 2015893 2015894 2015895 2015896 2015897 2015898 2015899 2015900 2015901 2015902 2015982 2015983 2015984 2015985 2015986 2015987
Blocks: 2010280
TreeView+ depends on / blocked
 
Reported: 2021-10-18 09:31 UTC by Petr Matousek
Modified: 2023-06-05 23:00 UTC (History)
54 users (show)

Fixed In Version:
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Doc Text:
A flaw was found in the way the dumpable flag setting was handled when certain SUID binaries executed its descendants. The prerequisite is a SUID binary that sets real UID equal to effective UID, and real GID equal to effective GID. The descendant will then have a dumpable value set to 1. As a result, if the descendant process crashes and core_pattern is set to a relative value, its core dump is stored in the current directory with uid:gid permissions. An unprivileged local user with eligible root SUID binary could use this flaw to place core dumps into root-owned directories, potentially resulting in escalation of privileges.
Clone Of:
Environment:
Last Closed: 2022-06-13 14:55:08 UTC
Embargoed:

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Description Petr Matousek 2021-10-18 09:31:26 UTC 
A flaw was found in the way dumpable flag setting was handled when certain SUID binaries executed it's descendants. The prerequisite is a SUID binary that sets real uid equal to effective uid, and real gid equal to effective gid. Then the descendant will have a dumpable value set to 1. As a result, if the descendant process crashes and core_pattern is set to a relative value, it's core dump is stored in the current directory with uid:gid permissions. An unprivileged local user with eligible root suid binary could use this flaw to place core dumps into root owned directories potentially resulting in escalation of privileges.

Reference:
https://www.openwall.com/lists/oss-security/2021/10/20/2
Comment 6 Petr Matousek 2021-10-20 14:38:13 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 2015987]
Comment 11 Wander 2021-12-28 17:17:39 UTC 
I proposed a patch in upstream for this bug https://lore.kernel.org/lkml/20211228170910.623156-1-wander@redhat.com/T/#t
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