Use-after-free in `clear` and `retain` when an element's `Drop` panics

Overview

SkipList::clear drops the node chain and only then resets tail and len. The drop runs each element's Drop, and T carries no bounds excluding a panicking one. If it unwinds, tail still points at the freed node while len stays non-zero.

back(), back_mut(), last_key_value() and last() dereference tail through unsafe, so reading the container after the unwind is a use-after-free (CWE-416). Drop for SkipList calls Box::from_raw on self.head, which clear already destroyed, so dropping the container is a double free (CWE-415).

retain, retain_mut and dedup_by reach the same state through Node::filter_rebuild, which frees nodes and runs a user predicate before the caller commits tail and len. There the head links are left partially rewired, so traversal can also reach freed nodes.

Mitigation

Update to 1.1.1.

Affected packages

• skiplist >= 0.0.0-0, < 1.1.1

Remediation

Upgrade to a patched release:

• skiplist 1.1.1