In affected versions, DTriangle::neighbor by order and DTriangle::vertex by order were public safe functions that accepted an arbitrary order value. These functions used order to access fixed-size internal arrays with get unchecked, without checking whether order was within bounds. Calling these methods with an out-of-bounds order could cause an out-of-bounds read from safe Rust code. This made the old APIs unsound, since safe callers could trigger undefined behavior without using unsafe.

The issue was fixed in version 0.29.0 as part of a broader rewrite that replaced the old triangle implementation with IntTriangle and removed the affected accessor methods.