Security readout for executives and security teams
Plain-English summary
CVE-2021-21781 is a Linux kernel information leak in ARM SIGPAGE handling. A local userland application may read data from the sigpage and expose kernel memory contents. The reported impact is confidentiality only, with no integrity or availability impact identified in the supplied sources.
Executive priority
Treat this as a moderate-priority confidentiality issue. It is not described as remotely exploitable or actively exploited, but shared ARM systems or environments running untrusted local workloads should be remediated promptly through normal kernel patching.
Technical view
The issue is mapped to CWE-908 and affects Linux Kernel v5.4.54 and v5.4.66, with the source noting 5.11-rc4 appeared vulnerable. The CVSS vector is local, low complexity, no privileges, no user interaction, and low confidentiality impact. Fixed kernel releases are listed as 4.14.222, 4.19.177, 5.4.99, 5.10.17, and 5.11.
Likely exposure
Exposure is most likely on ARM Linux systems running affected or unfixed kernel branches, particularly v5.4.54 or v5.4.66. Distribution backports can change risk, so apparent upstream version numbers alone may not prove vulnerability or safety.
Exploitation context
The bundle does not show CISA KEV listing or active exploitation evidence. Exploitation requires local code execution as a userland application and can disclose limited kernel memory contents. No remote attack path is described in the supplied sources.
Researcher notes
Evidence supports a local ARM SIGPAGE information disclosure with low confidentiality impact. The public bundle identifies upstream fixed releases but does not provide a complete distribution matrix. Validate exposure through vendor package metadata and avoid assuming all similarly numbered downstream kernels are vulnerable.
Mitigation direction
- Upgrade to a fixed kernel release listed by the CVE source.
- Check Linux distribution advisories for equivalent backported fixes.
- Review Oracle July 2022 CPU guidance for Oracle-managed environments.
- Prioritize ARM Linux hosts with local multi-user or untrusted-code exposure.
Validation and detection
- Inventory ARM Linux systems and record exact kernel builds.
- Check whether kernels include fixes from listed fixed releases.
- Confirm distro backport status with vendor security advisories.
- Review vulnerability scanner findings against actual package changelogs.
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-908: 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-2021-21781 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
- Medium
- CVSS
- 4 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
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:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N2.51.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
4MediumVector: CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1243CVE reference · x_refsource_MISC
- https://www.oracle.com/security-alerts/cpujul2022.htmlCVE reference · x_refsource_MISC
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 of Uninitialized Resource
Use of Uninitialized Resource represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.