# CVE-2026-28377: S3 SSE-C Encryption Key Exposed in Plaintext via Config Endpoint (CVE-2025-41118 Pattern)

> Attackers can retrieve S3 SSE-C encryption keys from the status config endpoint, exposing encrypted trace data.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Mar 2026
- **Updated:** 27 Aug 2026
- **Also known as:** CLEANSTART-2026-IH60054, CLEANSTART-2026-LM45189, CLEANSTART-2026-MG98376, CLEANSTART-2026-VL81811, ECHO-69d9-d5a1-7d86, GHSA-ffqx-q65f-36jf, GO-2026-5359, MINI-36mw-g675-43x2, MINI-4m3r-pp45-j64h, MINI-5g2p-jcqx-x3jw, MINI-5rqm-2mx5-xf4q, MINI-6whv-mj47-cf6g, MINI-79m3-25gj-89gh, MINI-7frh-jhfm-pg4h, MINI-7gpw-g5rf-cpvr, MINI-86wq-3h23-58jh, MINI-97hx-9jg6-cph4, MINI-9qc2-9c4p-crr4, MINI-cwp3-vxfg-6whh, MINI-j8p6-57qm-g9pp, MINI-phqc-8q3j-q3fm, MINI-pwmx-hx76-446w, MINI-qfhg-cf95-p92r, MINI-r294-4x54-f49f, MINI-rv54-m5mp-mj44, openSUSE-SU-2026:10390-1

## What is CVE-2026-28377?

CVE-2026-28377 is a high-severity vulnerability in Grafana Tempo, published on 26 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-326 (Inadequate Encryption Strength)

## Which versions are affected by CVE-2026-28377?

3 open source packages ship an affected version, including github.com/grafana/tempo. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/grafana/tempo` | Go | All versions | None |
| `github.com/grafana/tempo` | Go | All versions | 2.10.3 |
| `github.com/grafana/tempo` | Go | All versions | 2.10.3 |
| `tempo-cli` | openSUSE:Tumbleweed | All versions | 2.10.3-1.1 |

Products: Grafana Tempo.

## How do I fix CVE-2026-28377?

Upgrade github.com/grafana/tempo to 2.10.3 or later.

## Is CVE-2026-28377 being exploited?

There is no known exploitation of CVE-2026-28377 in the wild and no public exploit code.

## Other vulnerabilities in Grafana Tempo

- [CVE-2026-21728](https://insights.sbomify.com/CVE-2026-21728/): Tempo query limit results in unbounded memory allocation (high 7.5)
- [CVE-2026-27878](https://insights.sbomify.com/CVE-2026-27878/): Tempo TraceQL query with exemplar hint could result in unbounded memory usage (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28377 and fix it if it is affected.

What it is: CVE-2026-28377 is a high-severity vulnerability in Grafana Tempo, published on 26 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-28377 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/grafana/tempo (Go): affected all versions; no fix listed
- github.com/grafana/tempo (Go): affected all versions; fixed in 2.10.3
- github.com/grafana/tempo (Go): affected all versions; fixed in 2.10.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-28377/ (Markdown: https://insights.sbomify.com/CVE-2026-28377/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28377
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28377
- OSV: https://osv.dev/vulnerability/CVE-2026-28377

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-28377/
Summaries are generated and may contain mistakes; the official description above is the record.