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MEDIUM severity

zebrad has full node denial of service via non-ASCII LongPollId in getblocktemplateGHSA-qv2r-v3mx-f4pf

MEDIUM

GHSA-qv2r-v3mx-f4pf is a medium-severity (CVSS 6.5) CWE-248 vulnerability in zebra-rpc. A fix is available for zebra-rpc — see the affected versions and patch details below.

Also known asCVE-2026-52731
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Oct 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-qv2r-v3mx-f4pf.

EPSS Exploitation Probability

via FIRST.org ↗
0.5%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs44th percentile — riskier than 44% of all scored CVEsHighest risk
0.00%0.34%0.69%1.03%0.4%0.5%0.5%Sep 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-qv2r-v3mx-f4pf by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected
🦀zebra-rpc🦀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 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.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iozebra-rpcall versions8.0.0cargo update -p zebra-rpc --precise 8.0.0
🦀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-rpc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update zebra-rpc to 8.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qv2r-v3mx-f4pf 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.

Frequently Asked Questions

### 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-i
O3 Security · Impact-Aware SCA

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zebrad has full node denial of service via non-ASCII…