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Linux KernelOperating system · Linux

CVE-2021-3573

MEDIUM · 6.4 CVSS v3.1 Published 2021-08-13
Fix available
A fix is available. Upgrade to 5.13 or later.
See remediation →
66/100
Remediation priority · Elevated
Public exploit Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A use-after-free in function hci_sock_bound_ioctl() of the Linux kernel HCI subsystem was found in the way user calls ioct HCIUNBLOCKADDR or other way triggers race condition of the call hci_unregister_dev() together with one of the calls hci_sock_blacklist_add(), hci_sock_blacklist_del(), hci_get_conn_info(), hci_get_auth_info(). A privileged local user could use this flaw to crash the system or escalate their privileges on the system. This flaw affects the Linux kernel versions prior to 5.13-rc5.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-362

Two operations that should be atomic can interleave, so an attacker who wins a narrow timing window reaches an inconsistent, exploitable state. These bugs are subtle and easy to miss in review. Fixing them properly means correct locking or atomic operations around the shared resource.

General guidance for the race condition class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:< 5.13= 5.13
Enterprise LinuxOperating system
Affected:= 6.0= 7.0= 8.0
FedoraOperating system
Affected:= 34

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.13 or later
Fixed in 5.13
Vendor patch git.kernel.org →
Recommended fix High confidence

Linux Kernel 5.14 or later (or distribution-specific stable kernel backport that includes commit e305509e678b3a4af2b3cfd410f409f7cdaabb52)

  1. 1. Identify the current running kernel version using `uname -r`
  2. 2. Check your distribution's package manager for available kernel updates (e.g., `yum list kernel` or `dnf list kernel` for RHEL/Fedora)
  3. 3. Update the kernel package to version 5.14 or later, or to the latest available stable kernel that includes the fix
  4. 4. For RHEL/CentOS systems, enable the appropriate repository (e.g., RHEL 8 - `dnf update kernel`)
  5. 5. For Fedora 34, run `dnf update kernel` to install the fixed kernel
  6. 6. Reboot the system to load the new kernel: `systemctl reboot`
  7. 7. After reboot, verify the running kernel version with `uname -r` to confirm the fix is applied
Caveat Kernel upgrades may require system reboot and could introduce compatibility issues with third-party kernel modules; ensure custom drivers/modules are compatible with the new kernel version

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-3573 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data