GHSA-h749-fxx7-pwpg MinIO affected a DoS via Unbounded Memory Allocation in S3 Select CSV Parsing

• Go github.com/minio/minio: >= 0.0.0-20180815103019-7c14cdb60e53 (no fix yet)

Impact _What kind of vulnerability is it? Who is impacted?_ MinIO's S3 Select feature is vulnerable to memory exhaustion when processing CSV files containing lines longer than available memory. The CSV reader's `nextSplit()` function calls `bufio.Reader.ReadBytes('\n')` with no size limit, buffering the entire input in memory until a newline is found. A CSV file with no newline characters causes the entire contents to be read into a single allocation, leading to an OOM crash of the MinIO server process. This is exploitable by any authenticated user with `s3:PutObject` and `s3:GetObject` permissions. The attack is especially practical when combined with compression: a ~2 MB gzip-compressed CSV can decompress to gigabytes of data without newlines, allowing a small upload to cause large memory consumption on the server. However, compression is not required — a sufficiently large uncompressed CSV with no newlines triggers the same issue. Affected component: `internal/s3select/csv/reader.go`, function `nextSplit()`. CWE: CWE-770 (Allocation of Resources Without Limits or Throttling) Affected Versions All MinIO releases are through the final release of the minio/minio open-source project. The vulnerability was introduced in commit https://github.com/minio/minio/commit/7c14cdb60e53dbfdad2be644dfb180cab19fffa7, which added S3 Select support for CSV. The CSV reader has used unbounded line reads since this commit (originally via Go's stdlib `encoding/csv.Reader`, later via `bufio.Reader.ReadBytes` after a refactor in PR #8200. The first affected release is `RELEASE.2018-08-18T03-49-57Z`. Patches Fixed in: MinIO AIStor RELEASE.2025-12-20T04-58-37Z The fix replaces the unbounded `bufio.Reader.ReadBytes('\n')` call with a byte-at-a-time loop that caps line scanning at 128 KB (`csvSplitSize`). If no newline is found within this limit, the reader returns an error instead of continuing to buffer. Binary Downloads | Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio | | Linux | arm64 | minio | | macOS | arm64 | minio | | macOS | amd64 | minio | | Windows | amd64 | minio.exe | FIPS Binaries | Platform | Architecture | Download | | -------- | ------------ | --------------------------------------------------------------------------- | | Linux | amd64 | minio.fips | | Linux | arm64 | minio.fips | Package Downloads | Format | Architecture | Download | | ------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | DEB | amd64 | minio_20251220045837.0.0_amd64.deb | | DEB | arm64 | minio_20251220045837.0.0_arm64.deb | | RPM | amd64 | minio-20251220045837.0.0-1.x86_64.rpm | | RPM | arm64 | minio-20251220045837.0.0-1.aarch64.rpm | Container Images ```bash Standard docker pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z podman pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z FIPS docker pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z.fips podman pull quay.io/minio/aistor/minio:RELEASE.2025-12-20T04-58-37Z.fips ``` Homebrew (macOS) ```bash brew install minio/aistor/minio ``` Workarounds • Users of the open-source `minio/minio` project should upgrade to MinIO AIStor `RELEASE.2025-12-20T04-58-37Z` or later. If upgrading is not immediately possible: • Disable S3 Select access via IAM policy. Deny the `s3:GetObject` action with a condition restricting `s3:prefix` on sensitive buckets, or more specifically, deny `SelectObjectContent` requests at a reverse proxy by blocking `POST` requests with `?select&select-type=2` query parameters. • Restrict PutObject permissions. Limit `s3:PutObject` grants to trusted principals to reduce the attack surface. Note: this reduces risk but does not eliminate the vulnerability since any authorized user can exploit it. References • Introducing commit: `7c14cdb60` (PR #6127) • MinIO AIStor