Security Digest · Vulnerability record
CVE-2026-44498: Zebra's Block Validator Undercounts Coinbase and P2SH Sigops
ZEBRA is a Zcash node written entirely in Rust.
CVSS 9.2 Critical EPSS 0.4% · p31
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.4%, percentile 31: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 31% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
zebrad(crates.io (Rust)) < 4.4.0, fixed in 4.4.0. Check your lockfile, including transitive dependencies.
What it is
ZEBRA is a Zcash node written entirely in Rust. Prior to version 4.4.0, Zebra's block validator undercounts transparent signature operations against the 20000-sigop block limit (MAXBLOCKSIGOPS), 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. This issue has been patched in version 4.4.0.
From the GitHub advisory
Zebra's block validator undercounts transparent signature operations against the 20000-sigop block limit (MAXBLOCKSIGOPS), 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.
Weakness type: CWE-682.
Product: zebrad (crates.io (Rust)) · Assigned by: GitHub_M · Published: 2026-05-08
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| crates.io (Rust) | zebrad | < 4.4.0 | 4.4.0 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| ZcashFoundation | zebra | < 4.4.0 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 4.0 | 9.2 Critical | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N |
| GitHub | 4.0 | 9.2 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Attack requirements: none
- Privileges required: none (no login)
- User interaction: none
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.38% probability of exploitation activity in the next 30 days; percentile 31.
Timeline
- — GitHub-reviewed advisory GHSA-jv4h-j224-23cc published (critical)
- — CVE record published by GitHub_M
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-jv4h-j224-23cc github.com
- CVE.org record CVE-2026-44498 cve.org
- NVD entry CVE-2026-44498 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com
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