CVE-2026-28377 is a high-severity (CVSS 7.5) CWE-326 vulnerability in github.com/grafana/tempo. A fix is available for github.com/grafana/tempo — see the affected versions and patch details below.
S3 SSE-C Encryption Key Exposed in Plaintext via Config Endpoint (CVE-2025-41118 Pattern)
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-28377.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/grafana/tempoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
A vulnerability in Grafana Tempo exposes the S3 SSE-C encryption key in plaintext through the /status/config endpoint, potentially allowing unauthorized users to obtain the key used to encrypt trace data stored in S3.
Thanks to william_goodfellow for reporting this vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/grafana/tempo | all versions | 2.10.3go get github.com/grafana/tempo@v2.10.3 |
Affected Products
tempografanaDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/grafana/tempo, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/grafana/tempo to 2.10.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-28377 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Restrict network access to the Grafana Tempo service to trusted networks only. This will limit the ability of unauthorized remote attackers to access the `/status/config` endpoint and retrieve sensitive S3 encryption keys. Configure firewall rules to prevent external access to the Grafana Tempo service. This mitigation may impact legitimate access if not configured carefully. Ensure network restrictions persist across service reloads or system restarts.Source: Red Hat security advisory for CVE-2026-28377 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-28377 in your dependencies?
Find it across Go, including transitive dependencies.