RUSTSEC-2026-0403

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Source

https://rustsec.org/advisories/RUSTSEC-2026-0403

Import Source

https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2026-0403.json

JSON Data

https://api.osv.dev/v1/vulns/RUSTSEC-2026-0403

Published

2026-10-16T12:00:00Z

Modified

2026-10-26T14:00:05Z

Summary

Uninitialized memory exposed when streaming decompression of a legacy frame fails

Details

When decompression fails inside a legacy (zstd v0.4 to v0.7) frame, the bundled zstd library reports the output buffer as fully written although nothing was written. DCtx::decompress_stream committed that position even on error, and for a Vec<u8> destination this extended the vector's length over uninitialized memory.

Legacy support is enabled by default. A 5- or 6-byte corrupt legacy frame is enough: through zstd::stream::write::Decoder, up to 32 KiB of stale heap memory is then passed to the wrapped writer on the next write() or flush(), or when an auto_flush()/on_flush() decoder is dropped. Whether this reaches an attacker depends on where the application sends the decompressed output. zstd::stream::read::Decoder, zstd::decode_all and the bulk API are not affected.

Before zstd-safe 4.0.0, output buffers could only be initialized slices. The zstd crate's own writer had the same flaw from 0.4.22 to 0.7.x, which is covered by a separate advisory.

The flaw was corrected by only committing the buffer positions of a successful call.

Database specific

{
    "license":  "CC0-1.0"
}

References

Affected packages

crates.io / zstd-safe

Package

Name: zstd-safe; View open source insights on deps.dev
Purl: pkg:cargo/zstd-safe

Affected ranges

Type: SEMVER
Events: Introduced

4.0.0

Fixed

8.2.0

Ecosystem specific

{
    "affected_functions":  null,
    "affects":  {
        "arch":  [],
        "functions":  [
            "zstd_safe::DCtx::decompress_stream"
        ],
        "os":  []
    }
}