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CVE-2021-28964

19
FAUCET Score

CVE-2021-28964 is a race condition vulnerability in the Linux kernel's Btrfs filesystem, specifically affecting versions through 5.11.8, including Debian, Fedora, and NetApp products. This flaw allows a local attacker to trigger a denial of service (BUG) due to inadequate locking during a cloning operation. Rated Medium severity (CVSS 4.7), it requires low privileges and high attack complexity, but can lead to system unavailability. There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
<= 5.11.8CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
32CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.7MEDIUM

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
1.0
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.27%
Probability of exploitation in next 30 days
EPSS Percentile
18.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0027 is in the 61st percentile among its peer group of 1,297 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.4 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

microsoftpatch availablevia msrc
Product: 16920-16823Fixed in: 5.10.78.1-1
microsoftpatch availablevia msrc
Product: cbl2 kernel 5.10.78.1-1 on CBL Mariner 2.0Fixed in: 5.10.78.1-1
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: kernel
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: kernel-rt

Vendor Advisories (2)

redhatCVE-2021-28964Moderate

kernel: race condition in get_old_root function in fs/btrfs/ctree.c because of a lack of locking on an extent buffer before a cloning operation

Mar 16, 2021
microsoft2021-Mar/CVE-2021-28964Moderate

A race condition was discovered in get_old_root in fs/btrfs/ctree.c in the Linux kernel through 5.11.8. It allows attackers to cause a denial of service (BUG) because of a lack of locking on an extent buffer before a cloning operation aka CID-dbcc7d57bffc.

Mar 9, 2021

References

git.kernel.org / pub/scm/linux/kernel/git/torvalds/linux.git/commit
Mailing ListVendor Advisory
lists.debian.org / debian-lts-announce/2021/06/msg00019.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2021/06/msg00020.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/4VCKIOXCOZGXBEZMO5LGGV5MWCHO6FT3
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/PTRNPQTZ4GVS46SZ4OBXY5YDOGVPSTGQ
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/T2S3I4SLRNRUQDOFYUS6IUAZMQNMPNLG
security.netapp.com / advisory/ntap-20210430-0003
Third Party Advisory