Edgeless Systems Contrast panic in transit engine UnmarshalJSON

Severity: medium · CVSS 4.3 · Published 2026-07-01

A vulnerability in the Constrata coordinator transit engine allows an authenticated user to cause the service to crash internally by sending a specially crafted, short encrypted message. While the service automatically recovers from these crashes, an attacker can repeatedly trigger this behavior to flood system logs and degrade performance. This results in a minor service disruption and makes it harder for administrators to monitor legitimate system activity.

Technologies: Edgeless Systems Contrast, github.com/edgelesssys/contrast (Go). Vendors: Edgeless Systems, Go.

Quick answers

Is This vulnerability exploited in the wild?
No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?
Medium severity, with a CVSS score of 4.3, published 1 July 2026.
Which products and versions are affected?
Edgeless Systems Contrast <= 1.20.0; github.com/edgelesssys/contrast (Go) <= 1.20.0.
Is there a fix for This vulnerability?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is This vulnerability attacked?
It is attacked over the network, in a software library.
Am I affected?
Check whether you run Edgeless Systems Contrast or github.com/edgelesssys/contrast (Go) 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

A slice bounds out-of-range panic exists in the `ciphertextContainer.UnmarshalJSON` function within `coordinator/internal/transitengineapi/crypto.go`. The root cause is a lack of length validation on the decoded base64 ciphertext before attempting to extract a 12-byte AES-GCM nonce. An authenticated attacker with a valid mesh certificate can provide a ciphertext shorter than 12 bytes to trigger a Go runtime panic. While the `net/http` recovery mechanism prevents a full process crash, the panic results in a 500 error, connection termination, and the leakage of internal stack traces into the logs. This can be leveraged for log-based denial of service and version fingerprinting. The issue is addressed in version 1.21.0 by adding explicit length checks.

Affected products

  • edgelesssys contrast <= 1.20.0

Timeline

  • 2026-05-27: disclosed
  • 2026-07-01: advisory

References

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