🛡️ CVE-2026-52731 — zebra-rpc

⚪ Unknown ✅ No Known Exploit CWE-248 OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

zebrad has full node denial of service via non-ASCII LongPollId in getblocktemplate

Am I affected

You are affected if:

1. You run zebrad up to and including v4.4.1.

2. Your zebrad.toml sets rpc.listen_addr to a TCP address (RPC server is enabled).

3. An attacker can authenticate to the RPC endpoint. With the default enable_cookie_auth = true, this requires the attacker to read the .cookie file. With enable_cookie_auth = false, any network client reaching the RPC port can trigger it.

Summary

The getblocktemplate RPC handler panics when parsing a LongPollId parameter that contains non-ASCII (multi-byte UTF-8) characters. The handler performs byte-index string slicing on the user-supplied string, which panics in Rust when a byte index falls within a multi-byte character boundary. Because Zebra's release profile sets panic = "abort", the panic terminates the entire node process.

Details

The getblocktemplate handler receives a user-supplied LongPollId string and slices it at fixed byte offsets to extract the encoded tip hash and tip height. When the string contains multi-byte UTF-8 characters, a byte-index slice can land in the middle of a character, causing Rust's str indexing to panic with "byte index is not a char boundary."

Under the panic = "abort" release profile, this panic terminates the entire zebrad process rather than just the RPC task.

Patches

zebra-rpc 8.0.0 and zebrad 4.5.0.

Replace byte-index string slicing with character-aware parsing or validate that the LongPollId string contains only ASCII characters before slicing.

Workarounds

  • Disable the RPC server by removing rpc.listen_addr from zebrad.toml.
  • Ensure enable_cookie_auth = true (the default) and restrict filesystem access to the .cookie file.
  • Place a reverse proxy in front of the RPC port that validates LongPollId parameters are ASCII-only before forwarding.

Impact

A single authenticated RPC request terminates the zebrad process. Same impact profile as GHSA-c8w6-x74f-vmg3: repeatable on restart, affects mining pools and infrastructure that forward getblocktemplate calls.

Credit

Reported by @sangsoo-osec via a private GitHub Security Advisory submission.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Affected software

CVE-2026-52731 is recorded against 2 packages.

  • zebra-rpc
  • zebrad

Timeline and source

Published on 2 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

github.com (Web)
github.com (Package)
github.com (Web)

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE CWE-248
Public Exploit ✅ No
Source OSV
Published 2026-07-02
Updated 2026-08-12
Modified 2026-07-02
Fix URL N/A

Affected Packages

Software From version Fixed in
zebra-rpc — —
zebrad — —

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