--- id: "CVE-2026-44498" page: "https://infrastack.ai/live/CVE-2026-44498" kind: "vulnerability" aliases: ["CVE-2026-44498", "GHSA-jv4h-j224-23cc"] title: "Zebra's Block Validator Undercounts Coinbase and P2SH Sigops" severity: "critical" cvss: 9.2 epss: 0.00283 exploited: false status: "open" category: "package" products: [{"name": "zebrad", "fixed": ["4.4.0"], "affected": "< 4.4.0", "ecosystem": "cargo"}, {"name": "zfnd zebrad", "fixed": ["4.4.0"], "affected": "< 4.4.0", "ecosystem": "vendor"}] ecosystems: ["cargo", "vendor"] tags: ["cargo", "cwe-682", "package", "self-hosted", "zcash", "zebra"] not_affected_if: ["not-zcash-node", "zcashd-only"] published_at: "2026-05-07T20:54:33+00:00" first_seen_at: "2026-11-13T02:48:39+00:00" updated_at: "2026-11-13T03:13:22+00:00" sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-jv4h-j224-23cc", "first_seen_at": "2026-11-13T02:48:39+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44498", "first_seen_at": "2026-11-13T03:13:22+00:00"}] exploit_sources: [{"type": "epss", "score": 0.00283, "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-44498"}] --- # Zebra's Block Validator Undercounts Coinbase and P2SH Sigops Link for people: https://infrastack.ai/live/CVE-2026-44498 (this .md is for agents) Zebra's block validator undercounts transparent signature operations against the 20000 block limit, so it accepts blocks that zcashd rejects. A miner can use this to split the network, with Zebra nodes following a chain that zcashd nodes refuse. _Summary, check and fix written by a model from the sources; labelled as such._ ## Affected - cargo:zebrad affected < 4.4.0 fixed 4.4.0 - vendor:zfnd zebrad affected < 4.4.0 fixed 4.4.0 ## How to check - Check the installed Zebra version with `zebrad --version`; versions below `4.4.0` are affected. - Confirm whether the node validates blocks as a consensus participant, since the flaw only matters for nodes that accept blocks. ## Fix - Zebra: upgrade to `4.4.0` or later. ## Timeline - 2026-11-13T02:48:39+00:00 ghsa https://github.com/advisories/GHSA-jv4h-j224-23cc - 2026-11-13T03:13:22+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-44498 ## Documents - [advisory] Maintainer's advisory: api.github.com https://api.github.com/repos/ZcashFoundation/zebra/security-advisories/GHSA-jv4h-j224-23cc - [advisory] Maintainer's advisory: github.com https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-jv4h-j224-23cc - [fix] Release: github.com https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0 ## From the sources Zebra's block validator undercounts transparent signature operations against the 20000-sigop block limit (`MAX_BLOCK_SIGOPS`), allowing it to accept blocks that `zcashd` rejects with `bad-blk-sigops`. A miner who produces such a block can split the network: Zebra nodes follow the offending chain while `zcashd` nodes do not. Two distinct undercounts: #### A: Coinbase Hidden Legacy Sigops `zcashd`'s `GetLegacySigOpCount()` includes the coinbase input's `scriptSig`. Zebra's `Sigops` impl skipped the coinbase input entirely, so up to ~98 sigops (the 100-byte coinbase script length cap, less the height prefix) could be hidden inside the coinbase `scriptSig` without being charged against the block limit. #### B: Aggregate P2SH Sigops. `zcashd`'s `GetP2SHSigOpCount()` parses each P2SH input's redeem script with `accurate=true` and sums those sigops into the block-wide total via `ConnectBlock`. The check is per-block, not per-transaction, and the limit applies regardless of who mines the offending block — a miner just needs to include enough P2SH-spending transactions whose redeem scripts together exceed 20000 sigops. Zebra computed P2SH sigops only on the mempool-acceptance path (used for ZIP-317 weighting) and never accumulated them during block validation. A block whose aggregate redeem-script sigops exceed 20000 (e.g. 1334 P2SH spends × 15 sigops = 20010) would be accepted by Zebra and rejected by `zcashd`. ### Patches Fixed in this release: https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0. ### Workarounds None. Operators relying on Zebra for consensus should upgrade. ### Resources - `MAX_BLOCK_SIGOPS` constant inherited from Bitcoin via the Zcash protocol spec's §7.6 catch-all "Other rules inherited from Bitcoin", tracked for explicit documentation in [zcash/zips#568](https://github.com/zcash/zips/issues/568). - `zcashd` `GetLegacySigOpCount`: - `zcashd` `GetP2SHSigOpCount`: - `zcashd` `ConnectBlock` aggregates per-tx sigops and compares against `MAX_BLOCK_SIGOPS`. --- _Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_