T09 · Insecure Skill Coding Practices
- Location
scripts/meeting_windows.py:131- Finding
Unbounded Resource Consumption Through Unvalidated Step Size
- Content
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Vulnerability Details
File Location:
scripts/meeting_windows.py, lines 131 and 195–211
Vulnerability Type: Improper input validation leading to uncontrolled resource consumption
Risk Level: MediumVulnerable Code
python ap.add_argument("--step", type=int, default=60)python slots = [] t = start_day end_day = start_day + timedelta(days=1) while t < end_day: t2 = t + timedelta(minutes=args.duration) score = 0 reasons = [] rows = [] for p in participants: ls, le = t.astimezone(p.tz), t2.astimezone(p.tz) pref_start, pref_end = hours_map.get(p.name, default_hours) flex = me_flex if p.name in hours_map and (pref_start, pref_end) == hours_map.get(p.name) else "balanced" pen = penalty(ls, pref_start, pref_end, flex) score += pen r = reason_for_penalty(p.name, pen, ls) if r: reasons.append(r) rows.append((p.name, ls, le)) slots.append((classify(score), score, t, t2, rows, sorted(set(reasons)))) t += timedelta(minutes=args.step)Technical Analysis
The
--stepargument is parsed as an arbitrary integer but is never checked to ensure that it is positive. The loop terminates only whentreachesend_day, and its sole progress operation is:python t += timedelta(minutes=args.step)If
--step 0is supplied,tnever changes. If a negative step is supplied,tmoves farther away fromend_day. In both cases, the loop cannot terminate normally and continuously appends generated slot records to theslotslist.This creates an uncontrolled resource-consumption condition involving sustained CPU use and unbounded memory growth. The vulnerability is reachable directly through documented CLI execution when an untrusted caller can influence arguments.
Attack Path
- An attacker or untrusted caller invokes the meeting-window script.
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- Remediation
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Remediation Suggestions
Validate numeric CLI arguments before any processing. At minimum, require
--stepto be greater than zero. A reusableargparsevalidator can reject invalid input before entering the loop:python def positive_int(value: str) -> int: parsed = int(value) if parsed <= 0: raise argparse.ArgumentTypeError("value must be a positive integer") return parsed ap.add_argument("--step", type=positive_int, default=60) ap.add_argument("--duration", type=positive_int, default=60) ap.add_argument("--top", type=positive_int, default=3)Apply reasonable upper and lower bounds as appropriate for the intended interface. For example, constrain slot step and duration values to a supported scheduling range and cap the number of generated slots independently of user input.
Add a defensive iteration limit so future logic changes cannot create another unbounded loop:
python max_slots = 1440 generated = 0 while t < end_day and generated < max_slots: # Generate slot. t += timedelta(minutes=args.step) generated += 1Add automated tests confirming that zero and negative values are rejected promptly and do not start slot generation. If this CLI is invoked by a service, also enforce process-level timeouts and memory limits as defense in depth.