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High, CVSS 7.1amended

OpenAPI3 version value escapes emitterOutputDir and overwrites YAML/JSON outside the output tree

GHSA-2q42-4q24-7rgv

What to do

Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm @typespec/compiler

    Affected
    <= 1.15.0
    Fixed in
    no fixed version recorded

  • npm @typespec/openapi3

    Affected
    <= 1.15.0
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
7.1 · CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Summary The @typespec/openapi3 emitter retains the value of a @versioned enum member and interpolates it into the output filename as {version} without sanitizing path separators or traversal components. The completed path reaches the compiler's emitFile(), which creates the parent directory and writes the file without verifying containment under emitterOutputDir. A crafted declarative .tsp input can therefore create or overwrite an OpenAPI-formatted .yaml or .json file outside the configured output tree, subject to the compiler process's filesystem permissions. No executable TypeSpec extension or attacker-controlled JavaScript is required. Affected version Confirmed on: - @typespec/compiler 1.15.0 - @typespec/openapi3 1.15.0 - @typespec/http 1.15.0 - @typespec/versioning 0.85.0 - release tag commit f30cd352f93997e04c75d48c7ace6947a1d5d07a The critical openapi.ts and emitter-utils.ts blobs are unchanged on main commit 365ec52b50b82cd9e1e037de4c6fcd5de7e32e90 as checked on 2026-08-19.…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-2q42-4q24-7rgv

  2. Revision 2 · amended ·

    Amended from osv record GHSA-2q42-4q24-7rgv

  3. Revision 1 · created ·

    Published from ghsa record GHSA-2q42-4q24-7rgv

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-2q42-4q24-7rgv

Advisory: OpenAPI3 version value escapes `emitterOutputDir` and overwrites YAML/JSON outside the output tree
IDs: GHSA-2q42-4q24-7rgv
Record: https://patchnext.com/advisories/ghsa-2q42-4q24-7rgv (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @typespec/compiler: affected <= 1.15.0
- npm @typespec/openapi3: affected <= 1.15.0

## Suggested inspection (read-only)
- `npm ls @typespec/compiler --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @typespec/openapi3 --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @typespec/compiler, @typespec/openapi3.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2q42-4q24-7rgv (GitHub-reviewed advisory GHSA-2q42-4q24-7rgv lists affected ranges: npm @typespec/openapi3 >=0 =0 <=1.15.0)
- Verified: https://osv.dev/vulnerability/GHSA-2q42-4q24-7rgv (OSV record GHSA-2q42-4q24-7rgv lists affected ranges: npm @typespec/openapi3 >=0 =0 <=1.15.0)

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