CVE-2026-46644 Details
Description
Symfony Polyfill backports PHP features and provides compatibility layers for extensions and functions. From 1.17.1 until 1.38.1, symfony/polyfill-intl-idn accepts xn-- labels whose Punycode payload is empty or decodes to ASCII-only code points because Idn::process() does not enforce the UTS #46 revision 33 requirement that decoded ACE labels contain at least one non-ASCII code point. Originally unequal domain names can be regarded as equal, which can lead to blacklist bypassing, inconsistent URL parsing, and server-side request forgery in applications using the polyfill to canonicalise or compare hostnames. This issue is fixed in version 1.38.1.
A vulnerability exists in the Symfony Polyfill package, specifically in the 'polyfill-intl-idn' component, versions 1.17.1 prior to 1.38.1. The issue arises because the polyfill's 'Idn::process()' method accepts 'xn--' labels with Punycode payloads that are either empty or consist solely of ASCII characters. This acceptance violates the UTS #46 revision 33 requirement that such labels must contain at least one non-ASCII character. As a result, domain names that are originally unequal may be treated as equal, potentially leading to blacklist bypassing, inconsistent URL parsing, and server-side request forgery in applications that use the polyfill for hostname canonicalization or comparison.
Users can update to Symfony Polyfill version 1.38.1, which addresses this vulnerability by ensuring that 'xn--' labels are properly validated according to the UTS #46 revision 33 requirements.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No CVSS 3.x data is available for this CVE.
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jul 15, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-1289 | Improper Validation of Unsafe Equivalence in Input | [email protected] |
Affected Products
No affected product data is available for this CVE.
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 15, 2026 | CVE Modified | CISA-ADP |
| Jul 14, 2026 | New CVE Received | [email protected] |