# CVE-2026-41145: MinIO has an Unauthenticated Object Write via Query-String Credential Signature Bypass in Unsigned-Trailer Uploads > Attackers with a valid access key can write arbitrary objects to any bucket without a secret key or valid signature, bypassing authentication in MinIO. - **Severity:** High 8.8 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 22 Apr 2026 - **Updated:** 22 Apr 2026 - **Also known as:** GHSA-hv4r-mvr4-25vw, GO-2026-5437, ROOT-APP-GOBINARY-CVE-2026-41145 ## What is CVE-2026-41145? CVE-2026-41145 is a high-severity authentication bypass vulnerability in minio, published on 22 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description MinIO is a high-performance object storage system. Starting in RELEASE.2023-05-18T00-05-36Z and prior to RELEASE.2026-04-11T03-20-12Z, an authentication bypass vulnerability in MinIO's `STREAMING-UNSIGNED-PAYLOAD-TRAILER` code path allows any user who knows a valid access key to write arbitrary objects to any bucket without knowing the secret key or providing a valid cryptographic signature. Any MinIO deployment is impacted. The attack requires only a valid access key (the well-known default `minioadmin`, or any key with WRITE permission on a bucket) and a target bucket name. `PutObjectHandler` and `PutObjectPartHandler` call `newUnsignedV4ChunkedReader` with a signature verification gate based solely on the presence of the `Authorization` header. Meanwhile, `isPutActionAllowed` extracts credentials from either the `Authorization` header or the `X-Amz-Credential` query parameter, and trusts whichever it finds. An attacker omits the `Authorization` header and supplies credentials exclusively via the query string. The signature gate evaluates to `false`, `doesSignatureMatch` is never called, and the request proceeds with the permissions of the impersonated access key. This affects `PutObjectHandler` (standard and tables/warehouse bucket paths) and `PutObjectPartHandler` (multipart uploads). Users of the open-source `minio/minio` project should upgrade to MinIO AIStor `RELEASE.2026-04-11T03-20-12Z` or later. If upgrading is not immediately possible, block unsigned-trailer requests at the load balancer. Reject any request containing `X-Amz-Content-Sha256: STREAMING-UNSIGNED-PAYLOAD-TRAILER` at the reverse proxy or WAF layer. Clients can use `STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER` (the signed variant) instead. Alternatively, restrict WRITE permissions. Limit `s3:PutObject` grants to trusted principals. While this reduces the attack surface, it does not eliminate the vulnerability since any user with WRITE permission can exploit it with only their access key. Weakness: CWE-287 (Improper Authentication) ## Which versions are affected by CVE-2026-41145? 3 open source packages ship an affected version, including github.com/minio/minio. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `github.com/minio/minio` | Go | From 0.0.0-20230506025312-76913a9fd5c6 | None | | `github.com/minio/minio` | Go | From 0.0.0-20230506025312-76913a9fd5c6 to 0.0.0-20260212201848-7aac2a2c5b7c | None | | `github.com/minio/minio` | Go | From 0.0.0-20230506025312-76913a9fd5c6 to 0.0.0-20260212201848-7aac2a2c5b7c | None | Products: Minio Minio. ## How do I fix CVE-2026-41145? Upgrade to a fixed version. ## Is CVE-2026-41145 being exploited? There is no known exploitation of CVE-2026-41145 in the wild and no public exploit code. ## Other vulnerabilities in minio - [CVE-2023-28434](https://insights.sbomify.com/CVE-2023-28434/): MinIO Security Feature Bypass (high 8.8, exploited in the wild) - [CVE-2023-28432](https://insights.sbomify.com/CVE-2023-28432/): MinIO Information Disclosure (high 7.5, exploited in the wild) - [CVE-2020-11012](https://insights.sbomify.com/CVE-2020-11012/): Authentication bypass MinIO Admin API (critical 9.3) - [CVE-2026-33322](https://insights.sbomify.com/CVE-2026-33322/): MinIO: JWT Algorithm Confusion in OIDC Authentication (critical 9.2) - [CVE-2026-33419](https://insights.sbomify.com/CVE-2026-33419/): MinIO: LDAP login brute-force via user enumeration and missing rate limit (critical 9.1) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-41145 and fix it if it is affected. What it is: CVE-2026-41145 is a high-severity authentication bypass vulnerability in minio, published on 22 Apr 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-2026-41145 in the wild and no public exploit code. Affected packages and fixed versions: - github.com/minio/minio (Go): affected from 0.0.0-20230506025312-76913a9fd5c6; no fix listed - github.com/minio/minio (Go): affected from 0.0.0-20230506025312-76913a9fd5c6 up to 0.0.0-20260212201848-7aac2a2c5b7c; no fix listed - github.com/minio/minio (Go): affected from 0.0.0-20230506025312-76913a9fd5c6 up to 0.0.0-20260212201848-7aac2a2c5b7c; no fix listed 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-2026-41145/ (Markdown: https://insights.sbomify.com/CVE-2026-41145/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-41145 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41145 - OSV: https://osv.dev/vulnerability/CVE-2026-41145 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-41145/ Summaries are generated and may contain mistakes; the official description above is the record.