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Unratedamended

Out-of-bounds read in train_from_buffer when sample sizes overflow

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (zstd-safe 8.2.0, 7.4.0), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • crates.io zstd-safe

    Affected
    >= 0.0.0-0, < 7.4.0>= 8.0.0-0, < 8.2.0
    Fixed in
    7.4.0, 8.2.0

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
not scored
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

`ZDICT_trainFromBuffer` is never told the length of the samples buffer, so `train_from_buffer` checked that the sample sizes add up to it. With overflow checks off, as in release builds, that sum wrapped around: sizes totalling 2^64 plus the buffer length passed the check, and the trainer read past the end of the buffer. `zstd::dict::from_continuous` relies on this check from zstd 0.4.10; older versions of zstd had their own, covered by a separate advisory. This requires the sample sizes to come from an untrusted source. The flaw was corrected by summing the sizes with overflow checks.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from osv record RUSTSEC-2026-0401

  2. Revision 1 · created ·

    Published from osv record RUSTSEC-2026-0401

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: rustsec-2026-0401

Advisory: Out-of-bounds read in `train_from_buffer` when sample sizes overflow
IDs: rustsec-2026-0401
Record: https://patchnext.com/advisories/rustsec-2026-0401 (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 >= 0.0.0-0, < 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-2026-0401 (OSV record RUSTSEC-2026-0401 lists affected ranges: crates.io zstd-safe >=0.0.0-0 <8.2.0 (fixed))
- Verified: https://osv.dev/vulnerability/RUSTSEC-2026-0401 (OSV record RUSTSEC-2026-0401 lists affected ranges: crates.io zstd-safe >=0.0.0-0 =8.0.0-0 <8.2.0 (fixed))

Commands are suggestions: review each one before running it.

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