Security readout for executives and security teams
Plain-English summary
CVE-2021-31955 is a Windows kernel information disclosure flaw. A low-privileged local user could obtain sensitive kernel information. It is not described as remote code execution, but CISA lists it in KEV, so organizations should treat unpatched affected Windows systems as a real exposure.
Executive priority
Treat this as a priority patching item because it is in CISA KEV. The business risk is not broad remote compromise by itself, but it can help attackers already on a host gather sensitive information and support further intrusion activity.
Technical view
The CVSS vector indicates local attack, low complexity, low privileges, no user interaction, unchanged scope, and high confidentiality impact only. The affected set includes multiple Windows 10 and Windows Server 2019/2004/20H2 builds. Sources identify it as CWE-497 information exposure, with official remediation available through Microsoft guidance.
Likely exposure
Exposure is most likely on unpatched Windows 10 and Windows Server systems listed in the source bundle, especially older builds that missed June 2021 or later Microsoft security updates. Local access is required, so shared workstations, terminal servers, and compromised endpoints matter most.
Exploitation context
CISA KEV status supports known exploitation. The provided sources do not describe exploit mechanics, public exploit code, attacker groups, or whether exploitation was standalone or chained with other vulnerabilities.
Researcher notes
Do not overstate impact beyond information disclosure from the provided sources. The key constraints are local access and low privileges. The bundle does not identify affected kernel components, exploit primitives, indicators, or a standalone exploit path.
Mitigation direction
- Apply Microsoft security updates referenced in the MSRC advisory.
- Prioritize KEV-covered assets and internet-facing support infrastructure inventories.
- Reduce unnecessary local user access on affected systems until patched.
- Check Microsoft guidance for any product-specific prerequisites or supersedence details.
- Retire or isolate unsupported Windows builds that cannot receive fixes.
Validation and detection
- Inventory Windows versions and builds against the affected product list.
- Confirm relevant Microsoft security updates are installed on each affected host.
- Check vulnerability scanner results for CVE-2021-31955 coverage.
- Review endpoint telemetry for suspicious local post-compromise activity.
- Document exceptions for systems that cannot be patched immediately.
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-497: 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-2021-31955 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
- 5.5 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:F/RL:O/RC:C
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.
CISA KEV status
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:N/A:N/E:F/RL:O/RC:C1.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:F/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31955CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31955CVE reference · government-resource
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.
Exposure of Sensitive System Information to an Unauthorized Control Sphere
Exposure of Sensitive System Information to an Unauthorized Control Sphere represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.