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 (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. This issue has been patched in version 4.4.0.
https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-jv4h-j224-23cc
https://github.com/ZcashFoundation/zebra/releases/tag/v4.4.0
Published: 2026-05-08
Updated: 2026-05-08
Base Score: 7.8
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:C/A:N
Severity: High
Base Score: 7.5
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Severity: High
Base Score: 9.2
Vector: 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
Severity: Critical
EPSS: 0.0003