# CVE-2026-77298: SeaweedFS S3 OIDC Bearer authentication bypasses IAM role trust policy

> SeaweedFS S3 API allows federated users to bypass IAM trust policies and assume unauthorized roles, gaining read, write, and delete access to stored objects.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** BIT-seaweedfs-2026-77298, GHSA-757h-cm9x-wprg, MINI-jwm5-65w2-v6vh

## What is CVE-2026-77298?

CVE-2026-77298 is a high-severity authentication bypass vulnerability in seaweedfs, published on 26 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

SeaweedFS is a distributed storage system for files and blobs. In versions 4.39 and earlier, the S3 API accepts an external OIDC JWT sent directly in the Authorization header and maps it to an IAM role without enforcing that role's trust policy, so a federated user can assume a role they are not permitted to hold. The standard STS AssumeRoleWithWebIdentity path rejects such a token when the role's trust policy does not trust the token's federated provider, but the direct S3 bearer path validates only the token itself and then authenticates as the mapped role and evaluates that role's attached S3 permissions. As a result, a valid OIDC user whose token would be denied the role through STS can obtain the role's S3 access, including object read, write, and delete, by presenting the raw OIDC JWT directly to the S3 API. This issue is fixed in version 4.40

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-77298?

1 open source package ship an affected version, including seaweedfs.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `seaweedfs` | Bitnami | All versions | 4.40.0 |

## How do I fix CVE-2026-77298?

Upgrade seaweedfs to 4.40.0 or later.

## Is CVE-2026-77298 being exploited?

There is no known exploitation of CVE-2026-77298 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77298 and fix it if it is affected.

What it is: CVE-2026-77298 is a high-severity authentication bypass vulnerability in seaweedfs, published on 26 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77298 in the wild and no public exploit code.

Affected packages and fixed versions:
- seaweedfs (Bitnami): affected all versions; fixed in 4.40.0

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-2026-77298/ (Markdown: https://insights.sbomify.com/CVE-2026-77298/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77298
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77298
- OSV: https://osv.dev/vulnerability/CVE-2026-77298

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77298/
Summaries are generated and may contain mistakes; the official description above is the record.