CVE-2026-64777: Apple container build filesystem symlink escape

CVE-2026-64777 · Severity: medium · CVSS 4.3 · Published 2026-08-20

Apple's container build tool fails to properly validate symlinks during build context file synchronization, allowing a malicious builder peer to read files outside the build directory. An attacker with control over the builder image or BuildKit process could exploit this to disclose sensitive host files if the build context contains symlinks pointing outside its directory tree. This could expose credentials, configuration files, or other sensitive data during the build process.

Technologies: Apple Container. Vendors: Apple.

Quick answers

Is CVE-2026-64777 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-64777 being exploited in the wild.
How severe is CVE-2026-64777?
Medium severity, with a CVSS score of 4.3, published 20 August 2026.
Which products and versions are affected?
Apple Container <= 1.1.0.
Is there a fix for CVE-2026-64777?
A patch was published on 2026-08-12: Fixed in container version 1.2.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-64777 attacked?
It is attacked over the network.
Am I affected by CVE-2026-64777?
Check whether you run Apple Container at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is a path traversal/symlink escape in the BuildFSSync.read() and BuildFSSync.info() functions in Sources/ContainerBuild/BuildFSSync.swift. The host-side code performs lexical (textual) path validation to check if a requested filename is within the build context directory, but does not resolve symlinks before this check. A malicious builder peer can request a symlink by its in-context name, and the host will return the contents of whatever the symlink target resolves to, potentially outside the build context. The exploit requires two preconditions: a compromised or untrusted builder peer (via custom build.image configuration or supply-chain compromise) and a symlink in the build context pointing outside it. The stock builder does not exploit this except in a narrow startup race window. Fixed in container version 1.2.0 by resolving paths before validation.

Affected products

  • Apple container <= 1.1.0

Timeline

  • 2026-08-12: disclosed: GitHub Security Advisory GHSA-2v2q-4q35-h585 published
  • 2026-08-20: advisory: CVE-2026-64777 published on NVD
  • 2026-08-12: patched: Fixed in container version 1.2.0

References

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