CVE-2026-52731: Zebra rpc Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-qv2r-v3mx-f4pf",
  "modified" : "2026-07-02T19:28:03Z",
  "published" : "2026-07-02T19:28:03Z",
  "aliases" : [ "CVE-2026-52731" ],
  "summary" : "zebrad has full node denial of service via non-ASCII LongPollId in getblocktemplate",
  "details" : "### Am I affected\n\nYou are affected if:\n\n1. You run `zebrad` up to and including `v4.4.1`.\n2. Your `zebrad.toml` sets `rpc.listen_addr` to a TCP address (RPC server is enabled).\n3. An attacker can authenticate to the RPC endpoint. With the default `enable_cookie_auth = true`, this requires the attacker to read the `.cookie` file. With `enable_cookie_auth = false`, any network client reaching the RPC port can trigger it.\n\n### Summary\n\nThe `getblocktemplate` RPC handler panics when parsing a `LongPollId` parameter that contains non-ASCII (multi-byte UTF-8) characters. The handler performs byte-index string slicing on the user-supplied string, which panics in Rust when a byte index falls within a multi-byte character boundary. Because Zebra's release profile sets `panic = \"abort\"`, the panic terminates the entire node process.\n\n### Details\n\nThe `getblocktemplate` handler receives a user-supplied `LongPollId` string and slices it at fixed byte offsets to extract the encoded tip hash and tip height. When the string contains multi-byte UTF-8 characters, a byte-index slice can land in the middle of a character, causing Rust's `str` indexing to panic with \"byte index is not a char boundary.\"\n\nUnder the `panic = \"abort\"` release profile, this panic terminates the entire `zebrad` process rather than just the RPC task.\n\n### Patches\n\nzebra-rpc 8.0.0 and zebrad 4.5.0.\n\nReplace byte-index string slicing with character-aware parsing or validate that the `LongPollId` string contains only ASCII characters before slicing.\n\n### Workarounds\n\n- Disable the RPC server by removing `rpc.listen_addr` from `zebrad.toml`.\n- Ensure `enable_cookie_auth = true` (the default) and restrict filesystem access to the `.cookie` file.\n- Place a reverse proxy in front of the RPC port that validates `LongPollId` parameters are ASCII-only before forwarding.\n\n### Impact\n\nA single authenticated RPC request terminates the `zebrad` process. Same impact profile as GHSA-c8w6-x74f-vmg3: repeatable on restart, affects mining pools and infrastructure that forward `getblocktemplate` calls.\n\n### Credit\n\nReported by `@sangsoo-osec` via a private GitHub Security Advisory submission.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "zebra-rpc"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "8.0.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 7.0.0"
    }
  }, {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "zebrad"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.5.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.4.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-qv2r-v3mx-f4pf"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ZcashFoundation/zebra"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/Cargo.toml#L305"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-248" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-02T19:28:03Z",
    "nvd_published_at" : null
  }
}