Use-after-free of a dictionary after a one-shot call on a context with an open stream

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

The one-shot `DCtx` and `CCtx` methods assumed the C library resets the context, but it leaves an open stream as it is. When a stream was left unfinished on a context, a one-shot call such as `decompress_using_dict` could leave the context pointing at the dictionary borrowed for that call, and the next streaming call resumed the stream against it after it was freed: decompressed output then contained freed heap memory. On the compression side, the stream resumed against the one-shot call's buffers. This requires an application to use one context for both streaming and one-shot calls without a reset in between. The flaw was corrected by resetting the session after one-shot calls whenever a stream may be open.

Published by the source

16 Oct 2026, 12:00 UTC

Last modified by the source

2 Nov 2026, 09:30 UTC

Source last checked

3 Nov 2026, 06:10 UTC

1. Revision 2 · amended · 3 Nov 2026

   Amended from osv record RUSTSEC-2026-0400

2. Revision 1 · created · 27 Oct 2026

   Published from osv record RUSTSEC-2026-0400

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# Patch Next advisory brief: rustsec-2026-0400

Advisory: Use-after-free of a dictionary after a one-shot call on a context with an open stream
IDs: rustsec-2026-0400
Record: https://patchnext.com/advisories/rustsec-2026-0400 (revision 2, source checked 3 Nov 2026, 06:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: zstd-safe 8.2.0, 7.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io zstd-safe: affected >= 3.0.1, < 7.4.0; >= 8.0.0-0, < 8.2.0; fixed in 7.4.0, 8.2.0

## Suggested inspection (read-only)
- crates.io zstd-safe: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on zstd-safe.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0400 (OSV record RUSTSEC-2026-0400 lists affected ranges: crates.io zstd-safe >=3.0.1 <8.2.0 (fixed))
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0400 (OSV record RUSTSEC-2026-0400 lists affected ranges: crates.io zstd-safe >=3.0.1 =8.0.0-0 <8.2.0 (fixed))

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