Is This vulnerability exploited in the wild?

No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

How severe is This vulnerability?

Informational severity, published 16 October 2026.

Which products and versions are affected?

zstd-safe (crates.io) SEMVER:introduced=4.0.0,fixed=8.2.0; Zstd-Safe 4.0.0 to 8.1.x.

Is there a fix for This vulnerability?

Yes. zstd-safe (crates.io): upgrade to 8.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is This vulnerability attacked?

It is attacked with local access, in a software library.

Check whether you run zstd-safe (crates.io) or Zstd-Safe at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

zstd-safe OutBuffer::around_pos uninitialized memory exposure

Severity: info · Published 2026-10-16

zstd-safe is a Rust library that provides bindings to the Zstandard compression algorithm. A flaw in the OutBuffer::around_pos function allowed it to accept positions beyond the initialized memory of an internal buffer, causing the library to later mark uninitialized heap memory as valid, enabling safe Rust code to read stale data from the heap.

Technologies: zstd-safe (crates.io). Vendors: crates.io.

Quick answers

Is This vulnerability exploited in the wild?: No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?: Informational severity, published 16 October 2026.
Which products and versions are affected?: zstd-safe (crates.io) SEMVER:introduced=4.0.0,fixed=8.2.0; Zstd-Safe 4.0.0 to 8.1.x.
Is there a fix for This vulnerability?: Yes. zstd-safe (crates.io): upgrade to 8.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is This vulnerability attacked?: It is attacked with local access, in a software library.
Am I affected?: Check whether you run zstd-safe (crates.io) or Zstd-Safe at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

zstd-safe (crates.io): upgrade to 8.2.0 or later
```
cargo update -p zstd-safe
```

Technical details

The OutBuffer::around_pos function in zstd-safe versions 4.0.0 through 8.1.x accepted a position parameter that extended past the initialized length of a Vec<u8>, and subsequent streaming calls would mark all memory up to that position as initialized without zeroing the gap. This allowed safe Rust code to read uninitialized heap memory between the vector's previous length and the specified position. The fix zero-fills this gap to prevent information disclosure.

Affected products

zstd-safe 4.0.0 to 8.1.x

Timeline

2026-10-16: disclosed
2026-10-26: advisory

References

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