CVE-2026-52731 ZEBRA: Full node denial of service via non-ASCII LongPollId in getblocktemplate

What is CVE-2026-52731?

CVE-2026-52731 is a medium-severity denial of service vulnerability in ZcashFoundation zebra, published on 18 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

ZEBRA is a Zcash node written entirely in Rust. Prior to 4.5.0, an attacker authenticated to an enabled Zebra RPC endpoint can terminate zebrad by supplying a getblocktemplate LongPollId containing multi-byte UTF-8 characters. In zebra-rpc/src/methods/types/long_poll.rs, LongPollId::from_str originally checked the input byte length and then sliced fixed byte ranges to parse encoded fields. A slice boundary can land inside a multi-byte character and trigger Rust's byte index is not a char boundary panic. Zebra release builds use panic equals abort, so one malformed authenticated RPC request terminates the entire node process and can be repeated after restart. This issue is fixed in version 4.5.0.

Weakness: CWE-248

Which versions are affected by CVE-2026-52731?

4 open source packages ship an affected version, including zebra-rpc and zebrad.

How do I fix CVE-2026-52731?

Upgrade zebra-rpc to 8.0.0 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-52731 being exploited?

There is no known exploitation of CVE-2026-52731 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-qv2r-v3mx-f4pf.