CVE-2026-48853: Grpc Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-grp7-v8xh-rj7h",
  "modified" : "2026-08-25T18:09:53Z",
  "published" : "2026-08-25T18:09:53Z",
  "aliases" : [ "CVE-2026-48853" ],
  "summary" : "gRPC Erlang package vulnerable to Remote Code Execution with attacker-controlled gRPC payloads",
  "details" : "### Summary\n\n`GRPC.Codec.Erlpack.decode/2` calls `:erlang.binary_to_term/1` directly on the raw gRPC message body without the `:safe` option. Any unauthenticated peer that can reach a gRPC endpoint with `Content-Type: application/grpc+erlpack` can crash the entire BEAM node via atom table exhaustion or, if a decoded fun term flows into a call site that invokes it, achieve remote code execution inside the server process.\n\n### Details\n\n**Root cause** — `lib/grpc/codec/erlpack.ex` implements `decode/2` as a bare `:erlang.binary_to_term(binary)` call with no `:safe` flag, no size limit, and no type validation. This has two independent exploitation paths:\n\n**1. DoS via atom exhaustion** — BEAM atoms are never garbage-collected and the global atom table is bounded (~1,048,576 entries). A crafted payload encoding large numbers of fresh atoms saturates the table and crashes the entire VM, taking down all applications on the node.\n\n**2. RCE via fun materialization** — Without `:safe`, `binary_to_term/1` reconstructs fun and external-fun terms from wire data. If the decoded value reaches any call site that applies it (e.g. `Enum.map`, `Task.async`, direct invocation), attacker-controlled code executes inside the server process.\n\n**Configuration requirement:** `GRPC.Codec.Erlpack` is not registered by default and must be explicitly added to the server's `codecs` option.\n\n### PoC\n\n1. Start a gRPC server with `codecs: [GRPC.Codec.Erlpack]`.\n2. Open an HTTP/2 connection to the server.\n3. Send a gRPC-framed POST to any RPC path with `Content-Type: application/grpc+erlpack` and a body of `:erlang.term_to_binary(fn -> <malicious_code> end)`.\n4. The server's `decode/2` materializes the fun; any downstream call site that invokes the decoded value executes the attacker's code.\n5. For DoS only: send payloads encoding fresh atoms in a loop until the atom table is exhausted and the VM crashes.\n\n### Impact\n\nAffects `grpc` ≥ 0.4.0. Any server that explicitly registers `GRPC.Codec.Erlpack` is vulnerable to unauthenticated node-level DoS and potentially RCE.\n\n### References\n\n* Introduction commit: https://github.com/elixir-grpc/grpc/commit/25bcc569fe2cc4478531a6c546c923205fc751c9\n* Patch commit: https://github.com/elixir-grpc/grpc/commit/272a97a5ea1b46af1819f14a831fcf35fc91f992",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "grpc"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.4.0"
      }, {
        "fixed" : "1.0.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/elixir-grpc/grpc/security/advisories/GHSA-grp7-v8xh-rj7h"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-48853"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/elixir-grpc/grpc/pull/540"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/elixir-grpc/grpc/commit/272a97a5ea1b46af1819f14a831fcf35fc91f992"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-48853.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/elixir-grpc/grpc"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/elixir-grpc/grpc/releases/tag/v1.0.0"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-48853"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502", "CWE-770" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-25T18:09:53Z",
    "nvd_published_at" : "2026-06-15T23:16:45Z"
  }
}