Security readout for executives and security teams
Plain-English summary
CVE-2025-21173 is a high-severity Microsoft .NET elevation-of-privilege issue. It matters most on systems where affected .NET or Visual Studio versions are installed and untrusted local users can interact with developer or runtime environments.
Executive priority
Treat this as a high-priority patching item for development and build environments, especially where multiple users or contractors have local access. No active exploitation is cited in the supplied sources.
Technical view
The source data maps the flaw to CWE-379, indicating insecure temporary-file handling. CVSS 3.1 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.
Likely exposure
Exposure is most likely on endpoints, build servers, developer workstations, and application hosts running .NET 8.0, .NET 9.0, or listed Visual Studio 2022 versions before applying Microsoft guidance.
Exploitation context
The bundle does not show CISA KEV listing or confirmed active exploitation. CVSS exploit maturity is listed as unproven. The attack is local, requires low privileges and user interaction, and should not be treated as remotely exploitable from the supplied evidence.
Researcher notes
The record provides impact metrics, CWE-379, affected Microsoft products, and official remediation availability, but not root-cause detail, proof-of-concept status, or patched version numbers. Avoid assuming broader product impact beyond the listed .NET and Visual Studio versions.
Mitigation direction
- Apply Microsoft’s official updates for affected .NET and Visual Studio installations.
- Prioritize developer workstations, CI runners, build servers, and shared application hosts.
- Check MSRC guidance for exact fixed versions and installation requirements.
- Reduce unnecessary local user access on systems awaiting patching.
Validation and detection
- Inventory installed .NET runtimes, SDKs, and Visual Studio 2022 versions.
- Compare findings against Microsoft’s CVE-2025-21173 advisory.
- Confirm patch deployment through endpoint, server, and developer tooling management records.
- Document any systems that remain exposed and their compensating controls.
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-379: 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 lookupPrivilege 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-2025-21173 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.
SSVC decision data
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:C1.35.9microsoftVulnerability 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
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- .NET Elevation of Privilege VulnerabilityCVE reference, microsoft · vendor-advisory, patch
- https://www.herodevs.com/vulnerability-directory/cve-2025-21173CVE reference, CVE
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.
Creation of Temporary File in Directory with Insecure Permissions
Creation of Temporary File in Directory with Insecure Permissions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.