CVE-2026-44500 in Zebra
Summary
by MITRE • 05/08/2026
ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad version 4.4.0, prior to zebra-chain version 7.0.0, and prior to zebra-network version 6.0.0, several inbound deserialization paths in Zebra allocated buffers sized against generic transport or block-size ceilings before the tighter protocol or consensus limits were enforced. An unauthenticated or post-handshake peer could therefore force the node to preallocate and parse for orders of magnitude more data than the protocol intended, across headers messages, equihash solutions in block headers, Sapling spend vectors in V5/V4 transactions, and coinbase script bytes in blocks. This issue has been patched in zebrad version 4.4.0, zebra-chain version 7.0.0, and zebra-network version 6.0.0.
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Analysis
by VulDB Data Team • 05/08/2026
The vulnerability described represents a critical resource exhaustion issue affecting Zebra, a Zcash node implementation written in Rust. This flaw exists in the deserialization process of inbound network messages where the system allocates memory buffers based on generic transport or block-size ceilings rather than enforcing protocol-specific or consensus limits. The vulnerability affects multiple components including zebrad version prior to 4.4.0, zebra-chain version prior to 7.0.0, and zebra-network version prior to 6.0.0, creating a widespread impact across the node's network processing capabilities.
The technical implementation of this vulnerability stems from the improper buffer sizing logic within Zebra's inbound message handling. When processing network messages, the system preallocates memory buffers using generic ceiling values that are significantly larger than what the actual protocol specifications require. This design flaw allows malicious actors to exploit the gap between generic transport limits and specific protocol constraints by sending crafted messages that trigger excessive memory allocation. The vulnerability manifests across multiple message types including headers messages, equihash solutions within block headers, Sapling spend vectors in V5/V4 transactions, and coinbase script bytes in blocks, creating multiple attack vectors for resource exhaustion.
From an operational perspective, this vulnerability creates a severe denial-of-service condition where an unauthenticated or post-handshake peer can force the node to allocate and process orders of magnitude more data than intended by the protocol. The attacker can essentially consume system resources proportional to the generic ceiling values rather than the protocol-imposed limits, potentially leading to memory exhaustion, system instability, or complete node unavailability. This type of vulnerability aligns with CWE-770, which describes allocation of resources without limits or with inadequate limits, and represents a classic example of resource exhaustion attacks that can be classified under ATT&CK technique T1499.004 for network denial of service attacks.
The patch implemented in versions 4.4.0, 7.0.0, and 6.0.0 respectively addresses this issue by enforcing tighter protocol or consensus limits before buffer allocation occurs. This mitigation strategy ensures that memory buffers are sized according to actual protocol requirements rather than generic transport ceilings, preventing the excessive resource consumption that previously occurred. The fix represents a fundamental improvement in resource management and input validation within the Zebra node implementation, aligning with security best practices for preventing resource exhaustion attacks. The resolution demonstrates proper defensive programming principles where input validation and resource allocation are synchronized with protocol constraints to prevent attackers from manipulating system resources through malformed network messages.