Executive brief
Zebra, a software node for the Zcash cryptocurrency network, is vulnerable to a denial-of-service attack. An attacker can send specially crafted network messages that cause the software to consume excessive memory and crash. This can lead to service outages for Zcash node operators and disrupt network participation.
Technical details
A resource exhaustion vulnerability exists in Zebra's deserialization of 'addr' and 'addrv2' messages. The 'read_addr/addrv2' functions in 'codec.rs' used a maximum allocation limit derived from the 2 MiB total message size rather than the protocol-specified limit of 1,000 addresses. This allowed an attacker to trigger large memory allocations (up to 233,016 entries) before the software validated the actual address count. By sending multiple such messages over different network connections, an attacker can cause the Zebra process to abort due to out-of-memory (OOM) conditions. The issue is fixed in Zebra 4.3.1 and zebra-network 5.0.1 by enforcing the 1,000-address limit during the initial allocation phase.
Affected products
- Zcash Foundation zebrad < 4.3.1
- Zcash Foundation zebra-network < 5.0.1
Timeline
- 2026-04-17: disclosed
- 2026-04-18: advisory
- 2026-04-18: patched