Security readout for executives and security teams
Plain-English summary
This is a Linux kernel local privilege escalation flaw in NFC socket handling. A local attacker with CAP_NET_RAW in typical configurations could potentially gain higher privileges. It is serious for shared Linux hosts, containers with elevated network capabilities, and systems where untrusted local users or services run.
Executive priority
Treat as high priority where Linux systems host untrusted users or capability-bearing workloads. It is less urgent than a remote unauthenticated issue, but privilege escalation can turn an initial foothold into full system compromise.
Technical view
CVE-2021-23134 is a CWE-416 use-after-free in Linux kernel NFC LLCP socket bind/connect handling before 5.12.4. The CVSS 3.1 vector is local, low complexity, low privileges, no user interaction, with high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most relevant on Linux systems running affected kernels where local users, services, or containers have CAP_NET_RAW. Typical configurations require that capability, so internet-facing remote-only exposure is not supported by the provided evidence.
Exploitation context
The provided bundle does not show CISA KEV listing or cited active exploitation. The issue is local privilege escalation, not remote code execution. Practical risk depends on local access, kernel version, and whether CAP_NET_RAW is granted.
Researcher notes
Focus validation on NFC socket code exposure, kernel version lineage, and CAP_NET_RAW assignments. The source bundle identifies the upstream kernel commit and distribution advisories, but does not provide exploit-in-the-wild evidence.
Mitigation direction
- Update affected Linux kernels to vendor-fixed builds or Linux 5.12.4 or later.
- Apply relevant Fedora or Debian LTS security updates where those distributions are used.
- Restrict CAP_NET_RAW to trusted users, services, and containers only.
- Review vendor advisories for appliances or managed products using Linux kernels.
- Prioritize reboot coordination where kernel updates require it.
Validation and detection
- Inventory Linux kernel versions across servers, workstations, containers, and appliances.
- Compare installed kernels against vendor advisories and the 5.12.4 fixed-version boundary.
- Identify local users, services, or containers granted CAP_NET_RAW.
- Confirm patched kernels are running after updates, not merely installed.
- For NetApp environments, check the cited NetApp advisory for product-specific status.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-416: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-23134 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=c61760e6940dCVE reference · x_refsource_MISC
- https://www.openwall.com/lists/oss-security/2021/05/11/4CVE reference · x_refsource_MISC
- FEDORA-2021-286375de1eCVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-05152dbcf5CVE reference · vendor-advisory, x_refsource_FEDORA
- [debian-lts-announce] 20210623 [SECURITY] [DLA 2689-1] linux security updateCVE reference · mailing-list, x_refsource_MLIST
- [debian-lts-announce] 20210623 [SECURITY] [DLA 2690-1] linux-4.19 security updateCVE reference · mailing-list, x_refsource_MLIST
- https://security.netapp.com/advisory/ntap-20210625-0007/CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.