Vulnerability CVE-2021-3492

Vulnerability Name:

CVE-2021-3492 (CCN-200107)

Assigned:

2021-04-15

Published:

2021-04-15

Updated:

2021-05-21

Summary:

Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copy_from_user() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could use this to cause a denial of service (kernel memory exhaustion) or gain privileges via executing arbitrary code. AKA ZDI-CAN-13562.

CVSS v3 Severity:

7.8 High (CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
6.8 Medium (Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C)

Exploitability Metrics:	Attack Vector (AV): Local Attack Complexity (AC): Low Privileges Required (PR): Low User Interaction (UI): None
Scope:	Scope (S): Unchanged
Impact Metrics:	Confidentiality (C): High Integrity (I): High Availibility (A): High

8.4 High (CCN CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
7.3 High (CCN Temporal CVSS v3.1 Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C)

Exploitability Metrics:	Attack Vector (AV): Local Attack Complexity (AC): Low Privileges Required (PR): None User Interaction (UI): None
Scope:	Scope (S): Unchanged
Impact Metrics:	Confidentiality (C): High Integrity (I): High Availibility (A): High

CVSS v2 Severity:

7.2 High (CVSS v2 Vector: AV:L/AC:L/Au:N/C:C/I:C/A:C)

Exploitability Metrics:	Access Vector (AV): Local Access Complexity (AC): Low Authentication (Au): None
Impact Metrics:	Confidentiality (C): Complete Integrity (I): Complete Availibility (A): Complete

7.2 High (CCN CVSS v2 Vector: AV:L/AC:L/Au:N/C:C/I:C/A:C)

Exploitability Metrics:	Access Vector (AV): Local Access Complexity (AC): Low Athentication (Au): None
Impact Metrics:	Confidentiality (C): Complete Integrity (I): Complete Availibility (A): Complete

Vulnerability Type:

CWE-415
CWE-401

Vulnerability Consequences:

Gain Access

References:

Source: MITRE
Type: CNA
CVE-2021-3492

Source: MISC
Type: Third Party Advisory, VDB Entry
http://packetstormsecurity.com/files/162614/Kernel-Live-Patch-Security-Notice-LSN-0077-1.html

Source: XF
Type: UNKNOWN
ubuntu-cve20213492-code-exec(200107)

Source: MISC
Type: Mailing List, Patch, Vendor Advisory
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/focal/commit/?id=25c891a949bf918b59cbc6e4932015ba4c35c333

Source: MISC
Type: Mailing List, Patch, Vendor Advisory
https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/focal/commit/?id=8fee52ab9da87d82bc6de9ebb3480fff9b4d53e6

Source: CCN
Type: Ubuntu Web site
UBUNTU: SAUCE: shiftfs: free allocated memory in shiftfs_btrfs_ioctl_fd_replace() error paths

Source: CCN
Type: Ubuntu Web site
UBUNTU: SAUCE: shiftfs: handle copy_to_user() return values correctly

Source: CCN
Type: oss-sec Mailing List, Thu, 15 Apr 2021 14:33:06 -0700
[CVE-2021-3492] Ubuntu shiftfs Linux kernel file system double free vulnerability

Source: MISC
Type: Vendor Advisory
https://ubuntu.com/security/notices/USN-4917-1

Source: MISC
Type: Mailing List, Third Party Advisory
https://www.openwall.com/lists/oss-security/2021/04/16/2

Source: CCN
Type: ZDI-21-422
(Pwn2Own) Canonical Ubuntu ShiftFS File System Double Free Privilege Escalation Vulnerability

Source: MISC
Type: Third Party Advisory, VDB Entry
https://www.zerodayinitiative.com/advisories/ZDI-21-422/

Vulnerable Configuration:

Configuration 1:

cpe:/o:canonical:ubuntu_linux:*:*:*:*:lts:*:*:* (Version < 18.04)

OR cpe:/o:canonical:ubuntu_linux:*:*:*:*:lts:*:*:* (Version >= 18.04.1 and < 20.04)

Configuration 2:

cpe:/o:canonical:ubuntu_linux:*:*:*:*:-:*:*:* (Version < 20.10)

Configuration CCN 1:

cpe:/o:canonical:ubuntu:20.10:*:*:*:*:*:*:*

Denotes that component is vulnerable

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