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.