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Contras Affected by CopyFile Policy Subversion via Symlinks

High severity GitHub Reviewed Published Apr 23, 2026 in edgelesssys/contrast • Updated Apr 30, 2026

Package

github.com/edgelesssys/contrast (Go)

Affected versions

< 1.19.1

Patched versions

1.19.1

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

References

@burgerdev burgerdev published to edgelesssys/contrast Apr 23, 2026
Published to the GitHub Advisory Database Apr 30, 2026
Reviewed Apr 30, 2026
Last updated Apr 30, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Adjacent
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

Weaknesses

Improper Link Resolution Before File Access ('Link Following')

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-rh99-wc69-c255

Source code

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