CVE-2026-40881
MEDIUM
GHSA-xr93-pcq3-pxf8
Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
5DescriptionGitHub Advisory
CVE-2026-40881: addr/addrv2 Deserialization Resource Exhaustion
Summary
When deserializing addr or addrv2 messages, which contain vectors of addresses, Zebra would fully deserialize them up to a maximum length (over 233,000) that was derived from the 2 MiB message size limit. This is much larger than the actual limit of 1,000 messages from the specification. Zebra would eventually check that limit but, at that point, the memory for the larger vector was already allocated. An attacker could cause out-of-memory aborts in Zebra by sending multiple such messages over different connections.
Severity
Moderate - This is a Denial of Service Vulnerability that could allow an attacker to crash a Zebra node.
Affected Versions
All Zebra versions prior to version 4.3.1.
Description
The vulnerability exists in the read_addr/addrv2 functions in codec.rs. It deserializes a vector of addresses with the zcash_deserialize() trait method, which uses as a upper bound the result of T::max_allocation(). For theses types, it was derived from dividing the max message size (2 MiB) by the minimum serialized size of one entry. For AddrV1: 2_097_152 / 30 = 69,904. For AddrV2: 2_097_152 / 9 = 233,016. Only after deserialization was the MAX_ADDRS_IN_MESSAGE = 1000 limit checked.
An attacker could exploit this by:
- Creating
addroraddrv2messages with a large number of entries. - Submitting them to a Zebra node, possibly through multiple connections, to attempt to get Zebra into an out-of-memory state.
Impact
Denial of Service
- Attack Vector: Network.
- Effect: Zebra node crash.
- Scope: Any impacted Zebra node.
Fixed Versions
This issue is fixed in Zebra 4.3.1.
The fix changes the max_allocation() method for the relevant types to return 1,000, thus blocking larger values prior to deserialization.
Mitigation
Users should upgrade to Zebra 4.3.1 or later immediately.
There are no known workarounds for this issue. Immediate upgrade is the only way to ensure the node remains not vulnerable to the denial of service attack.
Credits
Thanks @Zk-nd3r for finding and reporting the issue, and suggesting the fix.
AnalysisAI
Zebra cryptocurrency node prior to version 4.3.1 allocates excessive memory (up to 233,016 addresses) when deserializing addr/addrv2 protocol messages, even though the specification limits messages to 1,000 addresses. An attacker can trigger out-of-memory crashes by sending multiple oversized address messages over different connections. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The vulnerability requires only that a Zebra node accepts peer-to-peer connections from the network and processes incoming addr or addrv2 messages, which is the default configuration for any Zebra node participating in the Zcash network. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine denial of service vulnerability with moderate real-world risk. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker crafts a Zcash protocol message (addr or addrv2) containing the maximum allowed serialized size (up to 2 MiB) with address entries, resulting in over 200,000 addresses in a single message. The attacker opens multiple TCP connections to a Zebra node and sends such oversized messages, causing the node to allocate excessive memory for deserialization (e.g., 233,016 addresses × ~9 bytes per address entry in addrv2). … |
| Remediation | Upgrade Zebra immediately to version 4.3.1 or later. … Detailed patch versions, workarounds, and compensating controls in full report. |
Threat intelligence, references, and detailed analysis are available after sign-in.
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External POC / Exploit Code
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