Security readout for executives and security teams
Plain-English summary
This vulnerability affects the GitHub Copilot plugin for JetBrains IDEs. The sources describe a command injection issue that could let an unauthenticated network attacker run code if a user interacts with the attack path. For organizations using JetBrains IDEs, treat this as a developer workstation and source-code protection issue.
Executive priority
High priority for engineering-heavy organizations. Developer machines often hold source code access, credentials, and build-system trust, so remote code execution in an IDE plugin can create business-critical downstream risk.
Technical view
CVE-2026-21516 is CWE-77 command injection in GitHub Copilot Plugin for JetBrains IDEs, listed as affecting version 1.0.0. CVSS 3.1 is 8.8 high, with network attack vector, low complexity, no privileges required, user interaction required, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most likely on developer machines running JetBrains IDEs with the affected GitHub Copilot plugin. The bundle only names version 1.0.0, so organizations should verify installed plugin versions against Microsoft guidance.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. CVSS indicates exploitation would require user interaction, but not attacker authentication. Exploit maturity is marked unproven in the provided vector.
Researcher notes
Evidence is limited to the CVE metadata and Microsoft advisory reference in the bundle. The provided data does not include exploit details, observed exploitation, or a fixed version number, so validation should anchor on current vendor guidance.
Mitigation direction
- Review the Microsoft MSRC advisory for the official patched version and guidance.
- Update the GitHub Copilot Plugin for JetBrains IDEs where vendor guidance applies.
- Inventory JetBrains IDE installations using the Copilot plugin.
- Temporarily restrict affected plugin use if patching cannot be confirmed.
- Prioritize developer systems with access to sensitive repositories or secrets.
Validation and detection
- Confirm whether JetBrains users have the GitHub Copilot plugin installed.
- Compare installed plugin versions against the MSRC advisory.
- Verify affected systems no longer run the listed vulnerable version.
- Check endpoint and software inventory records for remaining exposure.
- Record remediation status for developer workstations with repository access.
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-77: Command execution behavior lookup
Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-21516 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
- 8.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/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:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C2.85.9microsoftVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:N/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
- GitHub Copilot for Jetbrains Remote Code Execution VulnerabilityCVE reference, microsoft · vendor-advisory, patch
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.
Improper Neutralization of Special Elements used in a Command ('Command Injection')
Improper Neutralization of Special Elements used in a Command ('Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.