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msgpack

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2 actionable advisories, newest first. Withdrawn advisories and news are excluded. Coverage is partial.

  1. High, CVSS 7.5PyPIAmendedPublished

    MessagePack: Unbounded memory leak in msgpack C extension on strict_map_key validation failure

    CVE-2026-114613 · GHSA-j586-36cw-2gc2

    Affected
    • PyPI msgpack < 1.2.3
    Fixed in
    1.2.3· Vendor fix available
    Issue
    Impact The msgpack-python C extension (`msgpack._cmsgpack`) leaks a decoded map value when deserialization rejects a key with `strict_map_key=True` (the default). Repeated malformed inputs can cause unbounded process memory growth and denial of service in applications that deserialize attacker-controlled MessagePack data. Both `unpackb()` and the streaming `Unpacker` API are affected. The pure-Python fallback does not exhibit this leak in the reported tests. The report measured approximately 4 MiB retained per failed parse and 100 MiB after 25 failed parses on Windows with Python 3.14 and msgpack 1.2.2. These are reporter-provided results. Additional impact: stale parser-stack references The reference-ownership audit performed while fixing this leak found an additional memory-safety issue in the streaming `Unpacker`. After `unpack()` completed a nested container, an inactive parser-stack slot could retain a non-owning pointer to the decoded object. A subsequent `skip()` could…

    Recommended action: Upgrade to 1.2.3 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.

    Sources:github.com (1)osv.dev (2)Source checked Evidence →
  2. High, CVSS 7.5PyPIAmendedPublished

    MessagePack for Python: Out-of-bounds read / crash on Unpacker reuse after a caught error

    CVE-2026-57585 · GHSA-6v7p-g79w-8964

    Affected
    • PyPI msgpack <= 1.2.0
    Fixed in
    1.2.1· Vendor fix available
    Issue
    Impact If the Unpacker is used repeatedly after an error occurs, the process may crash with a SEGV. If the Unpacker is used repeatedly to unpack untrusted input from external sources, it may be vulnerable to a DoS attack. Patches v1.2.1 Workarounds Users should create a new Unpacker instead of reusing the same Unpacker after an error occurs. Applying the above patch can prevent SEGV, but reusing the Streaming Unpacker after it has encountered an error will not yield correct data. If an error occurs during Streaming Unpacking, the Stream and Streaming Unpacker should be discarded. Therefore, this is not just a workaround but the correct solution. The above patch only prevents crashes from incorrect usage.

    Recommended action: Upgrade to 1.2.1 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.

    Sources:osv.dev (1)github.com (2)Source checked Evidence →