RUSTSEC-2026-0406

Vulnerability from osv_rustsec – Published: 2026-10-16 12:00 – Updated: 2026-11-02 09:18 – Source website
VLAI
Summary
Use-after-free when changing a multithreaded context with an unfinished frame
Details

When a multithreaded frame (zstdmt feature, CParameter::NbWorkers) is left unfinished, its jobs may still be running on the worker threads: the C library only waits for them when the next frame starts, or when the context is freed. A session reset makes the context accept changes again in the meantime, so:

  • unloading the dictionary (load_dictionary, ref_cdict, ref_prefix, disable_dictionary, init*, or reset with parameters) freed the dictionary a worker was still compressing against;
  • changing NbWorkers made the next frame resize the job table before waiting for the old jobs.

The flaw was corrected by refusing these calls while a multithreaded frame is unfinished. The new CCtx::wait_for_workers() waits for the workers first.

References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "categories": [
          "memory-corruption"
        ],
        "cvss": null,
        "informational": "unsound"
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [
            "zstd_safe::CCtx::disable_dictionary",
            "zstd_safe::CCtx::init",
            "zstd_safe::CCtx::load_dictionary",
            "zstd_safe::CCtx::ref_cdict",
            "zstd_safe::CCtx::ref_prefix",
            "zstd_safe::CCtx::reset",
            "zstd_safe::CCtx::set_parameter"
          ],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "zstd-safe",
        "purl": "pkg:cargo/zstd-safe"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-0"
            },
            {
              "fixed": "7.4.0"
            },
            {
              "introduced": "8.0.0-0"
            },
            {
              "fixed": "8.2.0"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "When a multithreaded frame (`zstdmt` feature, `CParameter::NbWorkers`) is\nleft unfinished, its jobs may still be running on the worker threads: the C\nlibrary only waits for them when the next frame starts, or when the context\nis freed. A session reset makes the context accept changes again in the\nmeantime, so:\n\n- unloading the dictionary (`load_dictionary`, `ref_cdict`, `ref_prefix`,\n  `disable_dictionary`, `init*`, or `reset` with parameters) freed the\n  dictionary a worker was still compressing against;\n- changing `NbWorkers` made the next frame resize the job table before\n  waiting for the old jobs.\n\nThe flaw was corrected by refusing these calls while a multithreaded frame\nis unfinished. The new `CCtx::wait_for_workers()` waits for the workers\nfirst.",
  "id": "RUSTSEC-2026-0406",
  "modified": "2026-11-02T09:18:23Z",
  "published": "2026-10-16T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/zstd-safe"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0406.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gyscos/zstd-rs/commit/e224018a2389915d68ed17f30109bebad36e9734"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gyscos/zstd-rs/pull/384"
    }
  ],
  "related": [],
  "severity": [],
  "summary": "Use-after-free when changing a multithreaded context with an unfinished frame"
}



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