# CVE-2026-97731: Security feature bypass in MinIO

> Attackers can bypass signature verification to perform unauthorized server-side copies, reading data beyond the presigned URL's scope.

- **Severity:** High 7.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Sep 2026
- **Updated:** 25 Sep 2026
- **Also known as:** GHSA-r7wh-x6rf-8g63

## What is CVE-2026-97731?

CVE-2026-97731 is a high-severity vulnerability in MinIO, published on 25 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

MinIO through 7aac2a2 does not verify that every x-amz-* header present on a request also appears in the client-supplied X-Amz-SignedHeaders list. extractSignedHeaders() in cmd/signature-v4-utils.go iterates only the claimed list and never enumerates the headers that actually arrived, and thus a header that arrives unsigned is neither hashed into the canonical request nor rejected. Because cmd/api-router.go dispatches CopyObject on the presence of x-amz-copy-source alone, the holder of a presigned PUT URL scoped to a single object can add that header to the unmodified URL and cause a server-side copy, executed as the signer, of any object the signing key can read. A grant to write one object becomes a read of every bucket that key can reach. Amazon S3 rejects the equivalent request with HTTP 403 AccessDenied. The minio/minio GitHub repository was archived in April 2026; pgsty/silo before 1233254 is also affected.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-97731?


## How do I fix CVE-2026-97731?

No fix has been published for CVE-2026-97731 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-97731 being exploited?

There is no known exploitation of CVE-2026-97731 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97731 and fix it if it is affected.

What it is: CVE-2026-97731 is a high-severity vulnerability in MinIO, published on 25 Sep 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-2026-97731 in the wild and no public exploit code.

Affected product: MinIO. 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-2026-97731/ (Markdown: https://insights.sbomify.com/CVE-2026-97731/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97731
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97731
- OSV: https://osv.dev/vulnerability/CVE-2026-97731

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97731/
Summaries are generated and may contain mistakes; the official description above is the record.