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High, CVSS 8.2amended

tmp: Type-confusion bypass of _assertPath allows path traversal via non-string prefix/postfix/template

CVE-2026-49982GHSA-7c78-jf6q-g5cm

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (tmp 0.2.7), redeploy, then verify what is actually installed.

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 tmp

    Affected
    >= 0.2.6, < 0.2.7
    Fixed in
    0.2.7

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
EPSS
  • CVE-2026-49982: 0.50% estimated exploitation activity in the next 30 days; percentile 42.59 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary The assertPath guard added to tmp@0.2.6 rejects only string values that contain the substring ... It is bypassed when prefix, postfix, or template is supplied as a non-string value (Array, Buffer, or any object) whose includes('..') returns falsy but whose stringification still contains ../. The value flows through Array.prototype.join/String coercion inside generateTmpName and path.join(tmpDir, opts.dir, name), producing a final path that escapes tmpdir and creates a file or directory at an attacker-controlled location with the host process's privileges. This affects any application that forwards untrusted request data (a common pattern is JSON body fields or qs-parsed bracket-array query strings such as ?prefix[]=...) into tmp.file, tmp.fileSync, tmp.dir, tmp.dirSync, tmp.tmpName, or tmp.tmpNameSync without explicit type coercion. Impact - Arbitrary file creation outside the intended temporary directory, with the running process's filesystem permissions. - Directory…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-7c78-jf6q-g5cm

  2. Revision 1 · created ·

    Published from osv record GHSA-7c78-jf6q-g5cm

Agent brief

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# Patch Next advisory brief: CVE-2026-49982

Advisory: tmp: Type-confusion bypass of _assertPath allows path traversal via non-string prefix/postfix/template
IDs: CVE-2026-49982, GHSA-7c78-jf6q-g5cm
Record: https://patchnext.com/advisories/cve-2026-49982 (revision 2, source checked 26 Oct 2026, 12:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tmp 0.2.7. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm tmp: affected >= 0.2.6, < 0.2.7; fixed in 0.2.7

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

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on tmp.
- 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://osv.dev/vulnerability/GHSA-7c78-jf6q-g5cm (OSV record GHSA-7c78-jf6q-g5cm lists affected ranges: npm tmp >=0.2.6 <0.2.7 (fixed))
- Verified: https://github.com/advisories/GHSA-7c78-jf6q-g5cm (GitHub-reviewed advisory GHSA-7c78-jf6q-g5cm lists affected ranges: npm tmp >=0.2.6 <0.2.7)

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