twig/intl-extra: Unbounded formatter memoisation in keyed on template-controlled arguments
Date: 2026-05
Affected: composer/twig/intl-extra
Attack vector: dos
Category: vulnerability-disclosure
Severity: Low
CVE: CVE-2026-46629
CWE: CWE-770

### Description `IntlExtension` memoises every `\IntlDateFormatter` and `\NumberFormatter` it creates in instance-level arrays keyed on a hash that includes `locale`, `pattern`, `attrs` and other values that are ordinary named arguments of the `format_datetime` / `format_date` / `format_time` / `format_number` / `format_currency` filters. There is no size limit and no eviction. A template that iterates over many distinct `pattern` (or `locale`, or `grouping_used`, ...) values therefore allocates one ICU formatter object per distinct value and pins it for the entire lifetime of the `Twig\Environment`. Because ICU allocates its backing buffers outside the Zend memory manager, this growth is not bounded by `memory_limit`. On long-running runtimes (RoadRunner, Swoole, FrankenPHP worker mode, ReactPHP) where the `Environment` outlives a single request, the cache also accumulates across requests. ### Resolution The formatter caches are now bounded in size (100 entries each) and evict on a FIFO basis. ### Credits Twig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.


Mitigations:

Architectural layers (MAESTRO):