CVE-2023-28434

Workarounds

Browser API access must be enabled turning off MINIO_BROWSER=off allows for this workaround.

References

The vulnerable code:

// minio/cmd/generic-handlers.go
func setRequestValidityHandler(h http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    // ...
    // For all other requests reject access to reserved buckets
    bucketName, _ := request2BucketObjectName(r)
    if isMinioReservedBucket(bucketName) || isMinioMetaBucket(bucketName) {
      if !guessIsRPCReq(r) && !guessIsBrowserReq(r) && !guessIsHealthCheckReq(r) && !guessIsMetricsReq(r) && !isAdminReq(r) && !isKMSReq(r) {
        if ok {
          tc.FuncName = "handler.ValidRequest"
          tc.ResponseRecorder.LogErrBody = true
        }
        writeErrorResponse(r.Context(), w, errorCodes.ToAPIErr(ErrAllAccessDisabled), r.URL)
        return
      }
    }
    // ...

An attacker can use crafted requests to bypass metadata bucket name checking and put an object into any bucket while processing PostPolicyBucket. To carry out this attack, the attacker requires credentials with arn:aws:s3:::* permission, as well as enabled Console API access.

The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access. Typical impact: privilege escalation beyond the intended level.

CVE-2023-28434 has a CVSS score of 8.8 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.0.0-202303200415); upgrading removes the vulnerable code path.

Kodem intelligence

commit 67f4ba154a27a1b06e48bfabda38355a010dfca5
Author: Aditya Manthramurthy <[email protected]>
Date:   Sun Mar 19 21:15:20 2023 -0700

    fix: post policy request security bypass (#16849)

1. What is CVE-2023-28434? CVE-2023-28434 is a high-severity improper privilege management vulnerability in github.com/minio/minio (go), affecting versions < 0.0.0-202303200415. It is fixed in 0.0.0-202303200415. The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access.
2. How severe is CVE-2023-28434? CVE-2023-28434 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/minio/minio are affected by CVE-2023-28434? github.com/minio/minio (go) versions < 0.0.0-202303200415 is affected.
4. Is there a fix for CVE-2023-28434? Yes. CVE-2023-28434 is fixed in 0.0.0-202303200415. Upgrade to this version or later.
5. Is CVE-2023-28434 exploitable, and should I be worried? Whether CVE-2023-28434 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-28434 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-28434? Upgrade github.com/minio/minio to 0.0.0-202303200415 or later.