{"id":"GHSA-c8w6-x74f-vmg3","title":"zebrad vulnerable to full node denial of service via crafted Sapling receiver in z_listunifiedreceivers","summary":"zebrad vulnerable to full node denial of service via crafted Sapling receiver in z_listunifiedreceivers","severity":"medium","cvss":6.5,"cwe":["CWE-20","CWE-248","CWE-617","CWE-754"],"vendor":"zebra-rpc","product":"zebra-rpc","ecosystem":"rust","affected":["zebra-rpc <= 7.0.0","zebrad <= 4.4.1"],"patched":["zebra-rpc 8.0.0","zebrad 4.5.0"],"published":"2026-07-02","updated":"2026-07-02","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-c8w6-x74f-vmg3","references":[{"url":"https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-c8w6-x74f-vmg3"},{"url":"https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/Cargo.toml#L305"},{"url":"https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/zebra-rpc/src/methods.rs#L2867-L2914"},{"url":"https://github.com/advisories/GHSA-c8w6-x74f-vmg3"}],"tags":["ghsa","rust"],"ingestedAt":"2026-07-02T19:41:50.919Z","slug":"GHSA-c8w6-x74f-vmg3","body":"## Overview\n\n### 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 (typically local access). With `enable_cookie_auth = false`, any network client reaching the RPC port can trigger it.\n\n### Summary\n\nThe `z_listunifiedreceivers` RPC handler panics when processing a structurally valid Unified Address whose Sapling receiver carries 43 bytes that fail cryptographic validation (`sapling_crypto::PaymentAddress::from_bytes` returns `None` for non-subgroup Jubjub points). The handler calls `.expect(\"using data already decoded as valid\")` on the fallible result. Because Zebra's release profile sets `panic = \"abort\"`, the panic terminates the entire node process, not just the RPC task.\n\n### Details\n\n`zcash_address::unified::Encoding::decode` validates only the structural envelope of a Unified Address (F4Jumble, bech32m, typecode ordering, 43-byte length for Sapling). It does not validate that the embedded `pk_d` is a valid Jubjub subgroup point or that the diversifier produces a valid `g_d` preimage.\n\nAt `zebra-rpc/src/methods.rs:2893`, the handler calls `Address::try_from_sapling(network, data)`, which delegates to `sapling_crypto::PaymentAddress::from_bytes`. When `from_bytes` returns `None` (most random 32-byte strings fail the subgroup check), the `.expect()` fires and the process aborts.\n\nThe same crate already handles this correctly in `try_from_unified` at `zebra-chain/src/primitives/address.rs:99-110`, which returns `Err` when `from_bytes` fails. The vulnerable code path bypasses this validated route.\n\n### Patches\n\nzebra-rpc 8.0.0 and zebrad 4.5.0.\n\nReplace `.expect()` with `.map_err(|e| ErrorObject::owned(...))` for proper error propagation, or route through the existing `try_from_unified` path which already handles this case correctly.\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 rejects `z_listunifiedreceivers` calls with untrusted address parameters.\n\n### Impact\n\nA single authenticated RPC request terminates the `zebrad` process. The attack is repeatable on restart (the same request triggers the same abort), allowing an attacker to keep the node down indefinitely until the request is filtered upstream. Operators using `lightwalletd` backends, Zaino indexers, or mining pool infrastructure that forward RPC calls to `zebrad` may be exposed if the forwarding path passes through `z_listunifiedreceivers`.\n\n### Credit\n\nReported by `@robustfengbin` via a private GitHub Security Advisory submission.\n\n## Affected packages\n\n- `zebra-rpc <= 7.0.0`\n- `zebrad <= 4.4.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `zebra-rpc 8.0.0`\n- `zebrad 4.5.0`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}