# CVE-2026-45039: RustFS: Internode RPC HMAC secret falls back to public default credential, enabling peer impersonation

> Attackers can impersonate peers and escalate privileges in RustFS due to a hardcoded default HMAC secret used when no custom secret is configured.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 May 2026
- **Updated:** 30 May 2026
- **Also known as:** GHSA-r5qv-rc46-hv8q

## What is CVE-2026-45039?

CVE-2026-45039 is a critical vulnerability in rustfs, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

RustFS is a distributed object storage system built in Rust. Prior to 1.0.0-beta.2, the internode RPC layer authenticates every request with an HMAC-SHA256 signature using a shared secret. The function that produces this secret, get_shared_secret() in crates/ecstore/src/rpc/http_auth.rs, falls back to the public, source-tree-embedded DEFAULT_SECRET_KEY = "rustfsadmin" when neither the RUSTFS_RPC_SECRET environment variable nor the global S3 secret key has been configured. This vulnerability is fixed in 1.0.0-beta.2.

Weakness: CWE-798 (Use of Hard-coded Credentials), CWE-1392 (Use of Default Credentials)

## Which versions are affected by CVE-2026-45039?


## How do I fix CVE-2026-45039?

No fix has been published for CVE-2026-45039 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-45039 being exploited?

There is no known exploitation of CVE-2026-45039 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45039 and fix it if it is affected.

What it is: CVE-2026-45039 is a critical vulnerability in rustfs, published on 28 May 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-2026-45039 in the wild and no public exploit code.

Affected product: rustfs. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-45039/ (Markdown: https://insights.sbomify.com/CVE-2026-45039/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45039
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45039
- OSV: https://osv.dev/vulnerability/CVE-2026-45039

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45039/
Summaries are generated and may contain mistakes; the official description above is the record.