Use-after-free when changing a multithreaded context with an unfinished frame

{
  "id": "0170ccbf600e6b44e78e77cdf25c8bba82854f265f02077c00136eb3c7d0a8b3",
  "url": "https://osv.dev/vulnerability/RUSTSEC-2026-0406",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Use-after-free when changing a multithreaded context with an unfinished frame",
    "summary": "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.",
    "evidence": "osv:RUSTSEC-2026-0406",
    "products": [
      {
        "name": {
          "value": "zstd-safe",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "8.2.0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "RUSTSEC-2026-0406",
      "aliases": [
        "RUSTSEC-2026-0406"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0.0.0-0"
                },
                {
                  "fixed": "8.2.0"
                }
              ]
            }
          ],
          "package": {
            "name": "zstd-safe",
            "purl": "pkg:cargo/zstd-safe",
            "ecosystem": "crates.io"
          },
          "database_specific": {
            "cvss": null,
            "source": "https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2026-0406.json",
            "categories": [
              "memory-corruption"
            ],
            "informational": "unsound"
          },
          "ecosystem_specific": {
            "affects": {
              "os": [],
              "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"
              ]
            },
            "affected_functions": null
          }
        }
      ],
      "modified": "2026-10-26T14:00:05.095427051Z",
      "provider": "osv",
      "references": [
        "https://crates.io/crates/zstd-safe",
        "https://rustsec.org/advisories/RUSTSEC-2026-0406.html",
        "https://github.com/gyscos/zstd-rs/commit/e224018a2389915d68ed17f30109bebad36e9734",
        "https://github.com/gyscos/zstd-rs/pull/384"
      ],
      "provider_metadata": {
        "license": "CC0-1.0"
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 454196,
  "published_at": "2026-10-16T12:00:00+00:00"
}