Security readout for executives and security teams
Plain-English summary
CVE-2021-31204 is a high-severity elevation of privilege issue in Microsoft .NET and Visual Studio. It is most relevant to developer machines, build systems, and servers running affected .NET packages. The source bundle does not show active exploitation, but the potential impact is serious if a low-privileged local attacker can trigger the vulnerable path.
Executive priority
Treat this as a patch-priority engineering environment issue. It has high potential impact, but the provided sources do not show active exploitation or remote unauthenticated exposure. Prioritize systems where developers, build pipelines, or shared tooling run affected versions.
Technical view
The CVSS 3.1 score is 7.3 with local attack vector, low complexity, low privileges required, and user interaction required. Impact is rated high for confidentiality, integrity, and availability. Affected products include .NET Core 3.1, .NET 5.0.0, multiple Visual Studio 2019 versions, and related Fedora-packaged updates.
Likely exposure
Exposure is likely where affected .NET runtimes, SDKs, or Visual Studio 2019 builds remain installed, especially on developer workstations, CI agents, build servers, or Fedora systems carrying vulnerable .NET packages.
Exploitation context
The provided evidence does not indicate CISA KEV listing or confirmed active exploitation. The CVSS vector suggests exploitation requires local access, low privileges, and user interaction, so this is not described by the sources as a remote unauthenticated internet-facing issue.
Researcher notes
The source bundle provides severity, affected products, CVSS vector, and vendor advisory links, but little root-cause detail. No CWE is listed. Avoid assuming exploit mechanics, affected components beyond the listed products, or compensating controls not named by Microsoft or Fedora.
Mitigation direction
- Apply Microsoft guidance and updates for CVE-2021-31204.
- Apply relevant Fedora package updates where Fedora .NET packages are used.
- Remove unsupported or unnecessary affected .NET and Visual Studio versions.
- Prioritize developer workstations, build agents, and shared engineering hosts.
- Check vendor advisories for exact fixed versions before closure.
Validation and detection
- Inventory installed .NET Core, .NET 5, and Visual Studio 2019 versions.
- Compare installed versions against Microsoft MSRC guidance.
- Review Fedora package advisory status on Fedora systems.
- Confirm CI images and build agents no longer include affected packages.
- Document exceptions where vendor guidance cannot be applied 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.
Privilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-31204 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
- 7.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/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.
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:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C1.35.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.3HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31204CVE reference · x_refsource_MISC
- FEDORA-2021-a3c205f5b2CVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-13e3bd248fCVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-721731dc86CVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-c06b64b5eeCVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-f25eb9e302CVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-d551431950CVE reference · vendor-advisory, x_refsource_FEDORA
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.