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LOW severity

GHSA-h72h-ppcx-998p — zebra-network

LOW

GHSA-h72h-ppcx-998p is a low-severity (CVSS 3.7) vulnerability in zebra-network. A fix is available for zebra-network — see the affected versions and patch details below.

Zebra has pre-handshake buffer capacity reservation based on attacker-claimed body length

Published
Jul 2, 2026
Updated
Jul 2, 2026
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Jul 2, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

2 pkgs affected
🦀zebra-network🦀zebrad

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.

Description

Am I affected

You are affected if:

  1. You run zebrad up to and including v4.4.1.
  2. Your node accepts inbound P2P connections (network.listen_addr is set, which is the default).

Summary

The P2P codec's Codec::decode() method calls src.reserve(body_len + HEADER_LEN) after parsing a 24-byte protocol header, using the attacker-claimed body_len field. This reserves up to MAX_PROTOCOL_MESSAGE_LEN (~2 MiB) of virtual buffer capacity per connection before any body bytes arrive and before the handshake completes.

However, BytesMut::reserve() sets virtual capacity without committing physical memory pages. The operating system does not allocate physical RAM until bytes are actually written into the buffer. Since the attacker never sends body bytes, the reserved capacity remains uncommitted. Reproduction of the reporter's PoC (256 threads, 30 seconds of sustained connections) showed negligible RSS impact on the Zebra process.

Zebra's existing mitigations further constrain the practical attack surface: per-IP connection limits (max_connections_per_ip = 1), a per-connection accept rate of approximately one per second, and a 3-second handshake timeout that cleans up idle connections.

Details

At zebra-network/src/protocol/external/codec.rs:406, after parsing the 24-byte header and validating the network magic and body length against MAX_PROTOCOL_MESSAGE_LEN, the codec calls src.reserve(body_len + HEADER_LEN). The codec is constructed on the bare TCP stream before negotiate_version() runs, so the reservation is reachable from any TCP peer that can send 24 bytes.

No legitimate Zcash handshake message (version, verack) is anywhere close to 2 MiB. The codec makes no distinction between pre-handshake and post-handshake message types when sizing the reservation.

Patches

The fix defers large buffer reservations until after the handshake completes, or caps the per-message reservation for pre-handshake messages to what version/verack actually require.

Workarounds

No workaround is needed. The existing per-IP rate limiting, handshake timeout, and connection limits effectively mitigate the practical impact.

Impact

Minimal. The reservation affects virtual address space only, not physical memory. Zebra's existing connection-management mitigations (per-IP limits, accept rate, handshake timeout) further constrain the attack. The code path is worth cleaning up for defense-in-depth but does not produce a measurable denial-of-service effect.

Credit

Reported by @ouicate via a private GitHub Security Advisory submission.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iozebra-networkall versions7.0.0cargo update -p zebra-network --precise 7.0.0
🦀crates.iozebradall versions4.5.0cargo update -p zebrad --precise 4.5.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for zebra-network, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update zebra-network to 7.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-h72h-ppcx-998p is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-h72h-ppcx-998p can be triaged on real exposure rather than presence alone.

Tailored to GHSA-h72h-ppcx-998p. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Am I affected You are affected if: 1. You run `zebrad` up to and including `v4.4.1`. 2. Your node accepts inbound P2P connections (`network.listen_addr` is set, which is the default). ### Summary The P2P codec's `Codec::decode()` method calls `src.reserve(body_len + HEADER_LEN)` after parsing a 24-byte protocol header, using the attacker-claimed `body_len` field. This reserves up to `MAX_PROTOCOL_MESSAGE_LEN` (~2 MiB) of virtual buffer capacity per connection before any body bytes arrive and before the handshake completes. However, `BytesMut::reserve()` sets virtual capacity without c
O3 Security · Impact-Aware SCA

Is GHSA-h72h-ppcx-998p in your dependencies?

O3 Security finds GHSA-h72h-ppcx-998p across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

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GHSA-h72h-ppcx-998p: zebra-network | O3 Security