CVE-2026-52731

Summary

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

Severity

medium

CVSS

6.5

EPSS

0.4% (p31)

CWE

CWE-248

Also known as

GHSA-qv2r-v3mx-f4pf#zebra-rpc

Published

2026-07-02

Updated

2026-07-02

Advisory details

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.

References

• https://github.com/advisories/GHSA-qv2r-v3mx-f4pf
• https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-qv2r-v3mx-f4pf
• https://github.com/ZcashFoundation/zebra/blob/d4cd662c716382f6397d2a730148025a1ca79fec/Cargo.toml#L305

Related advisories

• GHSA-c8w6-x74f-vmg3#zebra-rpc — medium · crates.io/zebra-rpc
• CVE-2026-41585 — medium · crates.io/zebra-rpc
• CVE-2026-77078 — high · npm/multer
• CVE-2026-84445 — high · Go/google.golang.org/grpc
• CVE-2026-73088 — high · npm/browserslist
• CVE-2026-55484 — high · Go/github.com/guno1928/alos-http
• GHSA-pfvm-w89x-94jw — high · NuGet/SIPSorcery
• CVE-2026-13697 — high · npm/undici

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