oras-go: Arbitrary file write outside file.Store root via symlink-chain bypass in tar extraction (pushDir)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-85731: 0.68% estimated exploitation activity in the next 30 days; percentile 52.28 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The content/file.Store in oras-go v2 unpacks OCI layer tarballs when a descriptor carries io.deis.oras.content.unpack=true. The extraction routine validates symlink targets purely lexically (filepath.Join) and, for regular files placed directly at the extraction root, skips the parent-symlink Lstat walk. A malicious tarball can plant a chain of symlinks whose lexical target stays inside the extraction root but whose kernel-resolved target is any absolute path, then write through it with a follow-up regular-file entry. The result is arbitrary file create/overwrite outside the store's working directory under the default AllowPathTraversalOnWrite=false configuration — a canonical tar-slip → RCE primitive. Details Affected versions: <= v2.6.1 Entry point: content/file/file.go line 486, (Store).pushDir — reached from (Store).Push for any descriptor whose annotations include io.deis.oras.content.unpack: "true" (i.e. file.AnnotationUnpack) and an org.opencontainers.image.title.…

Published by the source

17 Sep 2026, 17:15 UTC

Last modified by the source

1 Oct 2026, 20:45 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m37j-52j7-pjw7

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6499

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m37j-52j7-pjw7

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# Patch Next advisory brief: CVE-2026-85731

Advisory: oras-go: Arbitrary file write outside file.Store root via symlink-chain bypass in tar extraction (pushDir)
IDs: CVE-2026-85731, GHSA-m37j-52j7-pjw7
Record: https://patchnext.com/advisories/cve-2026-85731 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: oras.land/oras-go/v2 2.6.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go oras.land/oras-go/v2: affected <= 2.6.1; fixed in 2.6.2

## Suggested inspection (read-only)
- Go oras.land/oras-go/v2: check the installed version with your package manager.

## 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 oras.land/oras-go/v2.
- 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-m37j-52j7-pjw7 (OSV record GHSA-m37j-52j7-pjw7 lists affected ranges: Go oras.land/oras-go/v2 >=0 <2.6.2 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6499 (OSV record GO-2026-6499 lists affected ranges: Go oras.land/oras-go/v2 >=0 <2.6.2 (fixed))
- Verified: https://github.com/advisories/GHSA-m37j-52j7-pjw7 (GitHub-reviewed advisory GHSA-m37j-52j7-pjw7 lists affected ranges: Go oras.land/oras-go/v2 >=0 <=2.6.1)

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