Contras Affected by CopyFile Policy Subversion via Symlinks

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Description

Impact

The Kata agent policies generated by the Contrast CLI had an issue in the CopyFile verification, which allowed arbitrary writes to the guest root filesytem. A malicious process on the host with the capability to connect to the Kata agent VSOCK could connect to the agent and issue a series of CopyFile requests to overwrite security-critical files or trick the workload into disclosing sensitive data, which effectively amounts to a full guest takeover.

Patches

This issue has been patched in Contrast v1.19.1.

Note that this fix does not change the fact that host-provided content is generally not trustworthy, as documented.

Workarounds

If upgrading is not possible, users can implement the fix in rego and pass it to contrast generate --policy. The rego-only fix is a bit trickier than the patch, because the data to check is binary. See the references for details.

Resources

  • Upstream GHSA: https://github.com/kata-containers/kata-containers/security/advisories/GHSA-q49m-57vm-c8cc
  • Alternative policy-only fix: https://gist.github.com/burgerdev/304dd0ab0fff1665b7c27e18a30cf96e

Basic information

Type
reviewed
Severity
high
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-04-30 20:57:17 UTC
Updated
2026-04-30 20:57:19 UTC
GitHub reviewed
2026-04-30 20:57:17 UTC

CVSS Scores

Base score Version Severity Vector
8.1 3.1 —
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

Type Value
GHSA GHSA-rh99-wc69-c255 ↗

CWEs

CWE id Name
CWE-59 Improper Link Resolution Before File Access ('Link Following')

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
go github.com/edgelesssys/contrast < 1.19.1 1.19.1 —

References

cvelogic Threat Intelligence