Impact A malicious peer acting as a state-sync source can crash a syncing node with a crafted "TrieChunk" whose proof contains a "TrieNodeChild" whose "suffix", when concatenated with the parent key via "KeyNibbles::Add", exceeds the fixed 63-byte backing array. "Add" ("primitives/src/key_nibbles.rs:332" / ":341") indexes "bytes[self.bytes_len()..self.bytes_len() + other.bytes_len()]" with no combined-length check, causing an out-of-bounds slice panic (both the even- and odd-length branches). "KeyNibbles" deserialization validates only the individual "length <= 126", not the combined parent + suffix length. The panic occurs at "put_chunk" → "child.key()" → "is_stump()" → "+", i.e. before "proof.verify()", so no valid proof is required. As with the related "child_index" issue, exploitation requires being the victim's sync peer during state sync, and the resulting crash is transient (the node restarts and re-syncs). Affected: core-rs-albatross <= 1.5.1 ("nimiq-primitives"). Patches Fixed in 1.6.0 via https://github.com/nimiq/core-rs-albatross/pull/3790 (commit "eabfc3e2"), which guards key-nibble concatenation against exceeding the maximum length instead of indexing out of bounds. Workarounds None other than syncing only from trusted peers. Upgrade to 1.6.0.