RUSTSEC-2026-0435 (CVE-2026-43868)

Vulnerability from osv_rustsec – Published: 2026-11-02 12:00 – Updated: 2026-11-02 11:45 – Source website
VLAI
Summary
Unbounded memory allocation in `thrift` binary protocol `read_bytes`
Details

Affected versions of the thrift crate size a buffer directly from an attacker-controlled 4-byte length read off the wire, before reading any payload and with no upper bound, allowing a hostile peer to force a large eager allocation or an immediate abort (denial of service, CWE-400 / CWE-789). This is the Rust implementation's instance of the CVE-2020-13949 pattern, published by the Apache Thrift PMC as CVE-2026-43868.

Details

In TBinaryInputProtocol::read_bytes (src/protocol/binary.rs), the length is read as a i32 from the transport and cast straight to usize to size a zeroing buffer before any payload is read:

fn read_bytes(&mut self) -> crate::Result<Vec<u8>> {
    let num_bytes = self.transport.read_i32::<BigEndian>()? as usize; // length from the wire
    let mut buf = vec![0u8; num_bytes];                               // unbounded eager allocation
    self.transport.read_exact(&mut buf).map(|_| buf).map_err(From::from)
}

There is no check that num_bytes is non-negative or that it fits within the data actually available:

  • A length of 0x7FFFFFFF forces a ~2 GiB allocation; 0x20000000 forces 512 MiB; and so on, from only a 4-byte input.
  • A negative length casts to a huge usize (up to usize::MAX), causing an immediate allocation failure / abort.

read_string routes through read_bytes, so string fields are affected the same way. The sink is reachable from any peer sending binary-protocol data, so this is an unauthenticated, network-reachable denial of service.

The fix

From thrift 0.23.0 onward, read_bytes goes through read_binary_len, which rejects negative sizes and enforces TConfiguration::max_string_size (default 100 MiB), alongside default message, frame, and recursion limits.

A separate, related gap on the non-strict message-name path was published as CVE-2026-58389 and fixed in 0.24.0; this advisory covers the read_bytes unbounded allocation (CVE-2026-43868), fixed in 0.23.0.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "categories": [
          "denial-of-service"
        ],
        "cvss": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
        "informational": null
      },
      "ecosystem_specific": {
        "affected_functions": null,
        "affects": {
          "arch": [],
          "functions": [
            "thrift::protocol::binary::TBinaryInputProtocol::read_bytes",
            "thrift::protocol::binary::TBinaryInputProtocol::read_string"
          ],
          "os": []
        }
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "thrift",
        "purl": "pkg:cargo/thrift"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-0"
            },
            {
              "fixed": "0.23.0"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "versions": []
    }
  ],
  "aliases": [
    "CVE-2026-43868"
  ],
  "database_specific": {
    "license": "CC0-1.0"
  },
  "details": "Affected versions of the `thrift` crate size a buffer directly from an attacker-controlled 4-byte length read off the wire, before reading any payload and with no upper bound, allowing a hostile peer to force a large eager allocation or an immediate abort (denial of service, CWE-400 / CWE-789). This is the Rust implementation\u0027s instance of the CVE-2020-13949 pattern, published by the Apache Thrift PMC as CVE-2026-43868.\n\n## Details\n\nIn `TBinaryInputProtocol::read_bytes` (`src/protocol/binary.rs`), the length is read as a `i32` from the transport and cast straight to `usize` to size a zeroing buffer **before** any payload is read:\n\n```rust\nfn read_bytes(\u0026mut self) -\u003e crate::Result\u003cVec\u003cu8\u003e\u003e {\n    let num_bytes = self.transport.read_i32::\u003cBigEndian\u003e()? as usize; // length from the wire\n    let mut buf = vec![0u8; num_bytes];                               // unbounded eager allocation\n    self.transport.read_exact(\u0026mut buf).map(|_| buf).map_err(From::from)\n}\n```\n\nThere is no check that `num_bytes` is non-negative or that it fits within the data actually available:\n\n- A length of `0x7FFFFFFF` forces a ~2 GiB allocation; `0x20000000` forces 512 MiB; and so on, from only a 4-byte input.\n- A negative length casts to a huge `usize` (up to `usize::MAX`), causing an immediate allocation failure / abort.\n\n`read_string` routes through `read_bytes`, so string fields are affected the same way. The sink is reachable from any peer sending binary-protocol data, so this is an unauthenticated, network-reachable denial of service.\n\n## The fix\n\nFrom `thrift` 0.23.0 onward, `read_bytes` goes through `read_binary_len`, which rejects negative sizes and enforces `TConfiguration::max_string_size` (default 100 MiB), alongside default message, frame, and recursion limits.\n\nA separate, related gap on the non-strict message-name path was published as CVE-2026-58389 and fixed in 0.24.0; this advisory covers the `read_bytes` unbounded allocation (CVE-2026-43868), fixed in 0.23.0.",
  "id": "RUSTSEC-2026-0435",
  "modified": "2026-11-02T11:45:44Z",
  "published": "2026-11-02T12:00:00Z",
  "references": [
    {
      "type": "PACKAGE",
      "url": "https://crates.io/crates/thrift"
    },
    {
      "type": "ADVISORY",
      "url": "https://rustsec.org/advisories/RUSTSEC-2026-0435.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.apache.org/thread/zj76dtwnbbs1m7z3focf4wd51pqpsmn9"
    }
  ],
  "related": [],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Unbounded memory allocation in `thrift` binary protocol `read_bytes`"
}



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