Vulnerability GHSA-g3hv-75wg-m249

minimatch 10.2.6 contains an attacker-controlled pattern amplification in firstPhasePreProcess() when optimizationLevel >= 2.

researcher: Reid Downing (b1nv0id) files:

• src/index.ts: 690-770
• src/index.ts: 780-796

issue: input-controlled growth of globParts during first-phase preprocessing, followed by quadratic second-phase processing.

the **/../ transformation clones a globparts entry and appends the clone to the same globparts array:

parts.splice(gs, 1)
const other = parts.slice(0)
other[gs] = '**'
globParts.push(other)

this occurs inside a do...while (didSomething) fixpoint loop, allowing generated entries to be processed again.

the expanded globparts array is subsequently processed by secondPhasePreProcess(), which performs pairwise comparisons:

for (let i = 0; i < globParts.length - 1; i++) {
  for (let j = i + 1; j < globParts.length; j++) {
    this.partsMatch(...)
  }
}

an attacker who can supply a glob pattern can therefore cause additional pattern entries to be generated during preprocessing, followed by quadratic pairwise processing, resulting in excessive cpu and memory consumption.