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hex_decode_unchecked AVX2 path reads past src

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (faster-hex 0.10.1), 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 faster-hex

    Affected
    >= 0.3.0, < 0.10.1
    Fixed in
    0.10.1

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.

`faster_hex::hex_decode_unchecked` is a safe function. On x86 and x86_64, when AVX2 is enabled, `hex_decode_avx2` keeps decoding while `dst.len() >= 32` and then loads 32 bytes from `src` and 32 bytes from `src[32..]`. Nothing in that loop requires `src` to contain 64 bytes. A safe caller can pass a short `src` and a `dst` of at least 32 bytes. The AVX2 load then reads outside `src`. The function has had this shape since 0.3.0. 0.10.0 is the last release with the unbounded AVX2 read. The maintainer agreed to this advisory and shipped the backport in 0.10.1 (pull request 74): the AVX2 loop now requires `src.len() >= 64` before those loads. 1.0.0 rewrites `hex_decode_unchecked` so the decoded length is `min(src.len() / 2, dst.len())`. Both are covered by `>= 0.10.1`. Other architectures take the scalar fallback and are outside this advisory.

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

    Published from osv record RUSTSEC-2026-0306

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-2026-0306

Advisory: `hex_decode_unchecked` AVX2 path reads past `src`
IDs: rustsec-2026-0306
Record: https://patchnext.com/advisories/rustsec-2026-0306 (revision 1, source checked 23 Oct 2026, 22:04 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: faster-hex 0.10.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io faster-hex: affected >= 0.3.0, < 0.10.1; fixed in 0.10.1

## Suggested inspection (read-only)
- crates.io faster-hex: 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 faster-hex.
- 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-2026-0306 (OSV record RUSTSEC-2026-0306 lists affected ranges: crates.io faster-hex >=0.3.0 <0.10.1 (fixed))

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