Open VSX 1.2.0 Blocks Marketplace Cache Poisoning
Tech GuruQuick Answer
The authority published GHSA-f55q-5m46-rmxc for Open VSX server, Docker, and GHCR packages from 0.6.0 before 1.2.0. Marketplace Takeover via Forwarded-host cache poisoning of /vscode/gallery/{namespace}/{extension}/latest. The advisory limits applicability to deployments that trust attacker-controlled forwarded-host data and have a cold cache entry. Affected deployments should be matched to the authority's exact scope and moved to the supported fixed release.
Confirm Scope And Apply The Supported Fix
What to do now: Inventory Open VSX server, Docker, and GHCR packages from 0.6.0 before 1.2.0, match the exact affected release or feature, apply the authority-supported fixed build or service remediation, validate the dependent workflow, and preserve evidence.
Last verified: 2026-09-21 UTC. Recheck the authoritative advisory and supported distribution channel before changing production.
Scope And Authority
| Product scope | Open VSX server, Docker, and GHCR packages from 0.6.0 before 1.2.0 |
|---|---|
| Advisory | GHSA-f55q-5m46-rmxc |
| CVE | CVE-2025-12999 |
| Authoritative release date | 2026-09-21 07:43:23 UTC |
| Authority revision date | 2026-09-21 07:43:23 UTC |
| Affected versions | Open VSX server, Docker, and GHCR packages from 0.6.0 before 1.2.0 |
| Fixed version | Open VSX 1.2.0 |
| CVSS base score | 9.1 (CVSS v4.0) |
| CVSS severity | Critical |
| Exploitation status | Not stated by the authority; no exploitation claim is inferred. |
What Changed
Marketplace Takeover via Forwarded-host cache poisoning of /vscode/gallery/{namespace}/{extension}/latest. The advisory limits applicability to deployments that trust attacker-controlled forwarded-host data and have a cold cache entry.
What To Validate Now
- Inventory. Locate Open VSX server, Docker, and GHCR packages from 0.6.0 before 1.2.0 deployments, versions, enabled features, exposure paths, owners, and dependent services.
- Establish applicability. Compare each deployment with the authority's affected-version statement: Open VSX server, Docker, and GHCR packages from 0.6.0 before 1.2.0 Do not infer applicability from product family or severity alone.
- Remediate. Apply Open VSX 1.2.0 through the supported vendor or project channel, following the current advisory and change-control requirements.
- Validate. Confirm the resulting version or managed-service state, exercise representative functionality and recovery paths, monitor for regressions, and document exceptions.
- Retain evidence. Preserve asset and owner identifiers, the applicability decision, before-and-after versions, change approval, installation output, validation results, and any exception or rollback record.
Operational Cautions
Use the exact supported release stream and repository. Test dependencies, clusters, integrations, and rollback before broad deployment; a CVSS rating or reachable feature is not evidence of exploitation.
Evidence To Retain
- Exact product, release stream, package or application version, enabled feature, environment, and accountable owner.
- UTC timestamps, authority revision, approved change record, installer or package-manager output, and resulting version.
- Relevant logs and monitoring evidence, test results, exceptions, compensating controls, and rollback decisions.
Related TechGeeks Resources
Authoritative References
Correction policy: If the authority changes affected versions, fixed versions, severity, exploitation information, mitigations, or required action, TechGeeks will update this notice and its verification date.
