CVE-2026-40881: Zcash Foundation Zebra resource exhaustion in addr message deserialization

CVE-2026-40881 · Severity: high · CVSS 7.5 · Published 2026-04-21

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.

Technologies: zebra-network (crates.io), zebrad (crates.io), Zfnd Zebrad. Vendors: crates.io, Zfnd.

Quick answers

Is CVE-2026-40881 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-40881 being exploited in the wild.
How severe is CVE-2026-40881?
High severity, with a CVSS score of 7.5, published 21 April 2026.
Which products and versions are affected?
zebra-network (crates.io) < 5.0.1, SEMVER:introduced=0,fixed=5.0.1; zebrad (crates.io) < 4.3.1, SEMVER:introduced=0,fixed=4.3.1.
Is there a fix for CVE-2026-40881?
Yes. zebra-network (crates.io): upgrade to 5.0.1 or later; zebrad (crates.io): upgrade to 4.3.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-40881 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-40881?
Check whether you run zebra-network (crates.io), zebrad (crates.io), Zfnd Zebra-Network or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • zebra-network (crates.io): upgrade to 5.0.1 or later
    cargo update -p zebra-network
  • zebrad (crates.io): upgrade to 4.3.1 or later
    cargo update -p zebrad

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

Identifiers

  • CVE-2026-40881
  • GHSA-xr93-pcq3-pxf8

Timeline

  • 2026-04-17: disclosed
  • 2026-04-18: advisory
  • 2026-04-18: patched

References

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