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Fix infinite loop when INTERVAL=0 in recurrence rules #67

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Fix infinite loop when INTERVAL=0 in recurrence rules #67

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415ffeb
Fix infinite loop when INTERVAL=0 in recurrence rules
anushka-codes1 Nov 11, 2025
15d4b05
Fix pre-commit issues
anushka-codes1 Nov 11, 2025
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1 change: 1 addition & 0 deletions news/interval-validation.bugfix
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Prevent infinite loop when INTERVAL=0 is used in recurrence rules by adding server-side validation. INTERVAL=0 is invalid per RFC 5545 and now returns a proper error message instead of causing the server to hang.
20 changes: 19 additions & 1 deletion src/plone/formwidget/recurrence/browser/json_recurrence.py
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Expand Up @@ -6,6 +6,7 @@
from plone.base.i18nl10n import name_formatvariables
from plone.base.i18nl10n import weekdayname_msgid
from plone.base.i18nl10n import weekdayname_msgid_abbr
from plone.formwidget.recurrence import _
from Products.Five import BrowserView
from zope.i18n import interpolate
from zope.i18n import translate
Expand Down Expand Up @@ -65,7 +66,24 @@ def json_string(self):
start_date = datetime.datetime(
int(data["year"]), int(data["month"]), int(data["day"])
)
rule = rrule.rrulestr(data["rrule"], dtstart=start_date)
# Validate the RRULE string to prevent invalid INTERVAL values
# INTERVAL=0 is invalid per RFC5545 and causes an infinite loop in
# python-dateutil when iterating the rule. Reject it early with a
# user-friendly, translated error message.
rrule_str = data["rrule"]
m = re.search(r"(?i)(?:^|;)INTERVAL\s*=\s*([-+]?[0-9]+)(?:;|$)", rrule_str)
if m:
try:
interval_val = int(m.group(1))
except Exception:
interval_val = None
if interval_val is not None and interval_val <= 0:
# Bad request: INTERVAL must be a positive integer
self.request.response.setStatus(400)
msg = translate(_("no_repeat_every"), context=self.request)
return {"error": msg}

rule = rrule.rrulestr(rrule_str, dtstart=start_date)
iterator = iter(rule)

if "batch_size" in data:
Expand Down