Privilege Escalation on Linux/MacOS

### Impact 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. ### Patches ``` commit 67f4ba154a27a1b06e48bfabda38355a010dfca5 Author: Aditya Manthramurthy <donatello@users.noreply.github.com> Date: Sun Mar 19 21:15:20 2023 -0700 fix: post policy request security bypass (#16849) ``` ### Workarounds Browser API access must be enabled turning off `MINIO_BROWSER=off` allows for this workaround. ### References The vulnerable code: ```go // 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 } } // ... ```

CVSS 3.1

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:H

Severity from

GitHub (reviewed advisory)

Weakness

CWE-269

Also known as

CVE-2023-28434

• github.com/minio/minio/security/advisories/GHSA-2pxw-r47w-4p8c
• nvd.nist.gov/vuln/detail/CVE-2023-28434
• github.com/minio/minio/pull/16849
• github.com/minio/minio/commit/67f4ba154a27a1b06e48bfabda38355a010dfca5
• github.com/minio/minio
• www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-28434