GHSA-443G-GWGP-49X4

Am I affected

You are affected if:

1. You run zebrad up to and including v4.4.1.
2. Your node accepts inbound P2P connections.

The read_getblocks and read_getheaders codec paths accepted block locator vectors up to approximately 65,535 entries (the generic TrustedPreallocate ceiling derived from MAX_PROTOCOL_MESSAGE_LEN), rather than the protocol-specification limit of 101 entries (matching zcashd's MAX_LOCATOR_SZ). Each entry in the locator vector triggers a per-hash chain lookup (HashMap::contains_key + RocksDB::contains_hash) in find_chain_intersection on a tokio blocking-pool thread.

A single maximally-sized getblocks message occupies one blocking-pool thread for approximately 10–65ms. Under sustained load from multiple peers, this can degrade state-read performance for block validation, RPC, and mempool lookups.

Details

The read_headers codec path already implements the correct pattern: it reads the CompactSize count, validates against MAX_HEADERS_PER_MESSAGE = 160 before deserialization, and rejects oversized messages. The read_getblocks and read_getheaders paths were missing this pre-deserialization count check and instead relied on the generic block::Hash::max_allocation() bound, which allows (MAX_PROTOCOL_MESSAGE_LEN - 1) / 32 = 65,535 hashes.

A legitimate block locator is logarithmic in chain length (approximately 30 hashes for the current ~3M-block Zcash chain). Zebra's own send-side cap is MAX_FIND_BLOCK_HASHES_RESULTS = 500.

The practical impact requires significant attacker bandwidth (approximately 2 MiB per request) and multiple Sybil peers to meaningfully degrade the blocking pool, which limits real-world exploitability.

Workarounds

No specific workaround is needed. Existing backpressure mechanisms (load shedding, sequential per-peer message processing, connection limits) constrain the practical impact.

Credit

Vulnerability identified by @dingledropper, who submitted the fix in PR #10570. Downstream CPU/blocking-pool impact analysis contributed by @ouicate.

Under sustained load from multiple Sybil peers, oversized locator vectors can occupy blocking-pool threads and degrade state-read performance. The effect is bounded by connection limits and requires significant attacker bandwidth.

The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.

GHSA-443G-GWGP-49X4 has a CVSS score of 3.7 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.5.0, 8.0.0); upgrading removes the vulnerable code path.

Kodem intelligence

Patched in Zebra 4.4.2. The fix caps block::Hash::max_allocation() at MAX_BLOCK_LOCATOR_LENGTH = 101, matching zcashd's MAX_LOCATOR_SZ. This causes the deserializer to reject oversized locators before any allocation or iteration occurs.

1. What is GHSA-443G-GWGP-49X4? GHSA-443G-GWGP-49X4 is a low-severity allocation of resources without limits or throttling vulnerability in zebrad (rust), affecting versions < 4.5.0. It is fixed in 4.5.0, 8.0.0. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
2. How severe is GHSA-443G-GWGP-49X4? GHSA-443G-GWGP-49X4 has a CVSS score of 3.7 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by GHSA-443G-GWGP-49X4?
   • zebrad (rust) (versions < 4.5.0)
   • zebra-chain (rust) (versions < 8.0.0)
4. Is there a fix for GHSA-443G-GWGP-49X4? Yes. GHSA-443G-GWGP-49X4 is fixed in 4.5.0, 8.0.0. Upgrade to this version or later.
5. Is GHSA-443G-GWGP-49X4 exploitable, and should I be worried? Whether GHSA-443G-GWGP-49X4 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-443G-GWGP-49X4 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-443G-GWGP-49X4?
   • Upgrade zebrad to 4.5.0 or later
   • Upgrade zebra-chain to 8.0.0 or later