GHSA-h749-fxx7-pwpg: MinIO affected a DoS via Unbounded Memory Allocation in S3 Select CSV Parsing
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 VersionsAll 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](https://github.com/minio/minio/pull/8200).The first affected release is `RELEASE.2018-08-18T03-49-57Z`.Patches**Fixed in**: MinIO AIStor RELEASE.2025-12-20T04-58-37ZThe 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](https://dl.min.io/aistor/minio/release/linux-amd64/minio)           |
| Linux    | arm64        | [minio](https://dl.min.io/aistor/minio/release/linux-arm64/minio)           |
| macOS    | arm64        | [minio](https://dl.min.io/aistor/minio/release/darwin-arm64/minio)          |
| macOS    | amd64        | [minio](https://dl.min.io/aistor/minio/release/darwin-amd64/minio)          |
| Windows  | amd64        | [minio.exe](https://dl.min.io/aistor/minio/release/windows-amd64/minio.exe) |FIPS Binaries| Platform | Architecture | Download                                                                    |
| -------- | ------------ | --------------------------------------------------------------------------- |
| Linux    | amd64        | [minio.fips](https://dl.min.io/aistor/minio/release/linux-amd64/minio.fips) |
| Linux    | arm64        | [minio.fips](https://dl.min.io/aistor/minio/release/linux-arm64/minio.fips) |Package Downloads| Format | Architecture | Download                                                                                                                            |
| ------ | ------------ | ----------------------------------------------------------------------------------------------------------------------------------- |
| DEB    | amd64        | [minio_20251220045837.0.0_amd64.deb](https://dl.min.io/aistor/minio/release/linux-amd64/minio_20251220045837.0.0_amd64.deb)         |
| DEB    | arm64        | [minio_20251220045837.0.0_arm64.deb](https://dl.min.io/aistor/minio/release/linux-arm64/minio_20251220045837.0.0_arm64.deb)         |
| RPM    | amd64        | [minio-20251220045837.0.0-1.x86_64.rpm](https://dl.min.io/aistor/minio/release/linux-amd64/minio-20251220045837.0.0-1.x86_64.rpm)   |
| RPM    | arm64        | [minio-20251220045837.0.0-1.aarch64.rpm](https://dl.min.io/aistor/minio/release/linux-arm64/minio-20251220045837.0.0-1.aarch64.rpm) |Container ImagesHomebrew (macOS)Workarounds[Users of the open-source `minio/minio` project should upgrade to MinIO AIStor `RELEASE.2025-12-20T04-58-37Z` or later.](https://docs.min.io/enterprise/aistor-object-store/upgrade-aistor-server/community-edition/)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.ReferencesIntroducing commit: [`7c14cdb60`](https://github.com/minio/minio/commit/7c14cdb60e53dbfdad2be644dfb180cab19fffa7) ([PR #6127](https://github.com/minio/minio/pull/6127))[MinIO AIStor](https://min.io/aistor)
CVSS v4.0: 7.1