Publish GHSA-2xf4-cg6j-vhgq

Author: advisory-database[bot]

advisories/github-reviewed/2026/05/GHSA-2xf4-cg6j-vhgq/GHSA-2xf4-cg6j-vhgq.json

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+{
+  "schema_version": "1.4.0",
+  "id": "GHSA-2xf4-cg6j-vhgq",
+  "modified": "2026-05-28T19:52:36Z",
+  "published": "2026-05-28T19:52:36Z",
+  "aliases": [
+    "CVE-2026-46644"
+  ],
+  "summary": "symfony/polyfill-intl-idn: xn-- labels with ASCII-only Punycode payloads are treated as equivalent to their decoded form",
+  "details": "### Description\n\n`symfony/polyfill-intl-idn` provides a userland implementation of `idn_to_utf8()` and `idn_to_ascii()` for runtimes that lack the `intl` extension. Its `Idn::process()` method decodes labels prefixed with `xn--` using Punycode but never enforces the validity criterion added in UTS #46 revision 33 Section 4 step 4.1.2: after a successful Punycode decode, the result must contain at least one non-ASCII code point.\n\nAs a consequence, `xn--` labels whose Punycode payload is empty (`xn--`) or decodes to a string made of only ASCII code points (e.g. `xn--kc1zs4-`) are accepted by the polyfill while PHP's native `ext-intl` rejects them with `IDNA_ERROR_INVALID_ACE_LABEL`. Originally unequal domain names are therefore regarded as equal, which can lead to blacklist bypassing, inconsistent URL parsing and server-side request forgery (similar to CVE-2024-12224).\n\nExample with `IDNA_USE_STD3_RULES | IDNA_CHECK_BIDI | IDNA_CHECK_CONTEXTJ | IDNA_NONTRANSITIONAL_TO_ASCII`:\n\n| Input | Polyfill output | Native `ext-intl` output |\n| --- | --- | --- |\n| `poc.xn--kc1zs4-.com` | `poc.kc1zs4.com` | `false` (`errors=1024`) |\n| `poc.kc1zs4.xn--` | `poc.kc1zs4.` | `false` (`errors=1024`) |\n\nApplications using the polyfill to canonicalise or compare hostnames inherit the inconsistency.\n\n### Resolution\n\n`Idn::process()` now records `IDNA_ERROR_INVALID_ACE_LABEL` when a Punycode payload decodes to an empty string or to a string containing only ASCII code points, matching the native `ext-intl` behaviour and UTS #46 revision 33.\n\nThe patch for this issue is available [here](https://github.com/symfony/polyfill/commit/1be936e2491ccebe152bd736dfc91eb1422c8bec) for branch 1.x.\n\n### Credits\n\nSymfony would like to thank Nazy Mad for reporting the issue and Nicolas Grekas for providing the fix.",
+  "severity": [
+    {
+      "type": "CVSS_V4",
+      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:U"
+    }
+  ],
+  "affected": [
+    {
+      "package": {
+        "ecosystem": "Packagist",
+        "name": "symfony/polyfill"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "1.17.1"
+            },
+            {
+              "fixed": "1.38.1"
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "package": {
+        "ecosystem": "Packagist",
+        "name": "symfony/polyfill-intl-idn"
+      },
+      "ranges": [
+        {
+          "type": "ECOSYSTEM",
+          "events": [
+            {
+              "introduced": "1.17.1"
+            },
+            {
+              "fixed": "1.38.1"
+            }
+          ]
+        }
+      ]
+    }
+  ],
+  "references": [
+    {
+      "type": "WEB",
+      "url": "https://github.com/symfony/polyfill/security/advisories/GHSA-2xf4-cg6j-vhgq"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/symfony/polyfill/commit/1be936e2491ccebe152bd736dfc91eb1422c8bec"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/polyfill-intl-idn/CVE-2026-46644.yaml"
+    },
+    {
+      "type": "WEB",
+      "url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/polyfill/CVE-2026-46644.yaml"
+    },
+    {
+      "type": "PACKAGE",
+      "url": "https://github.com/symfony/polyfill"
+    },
+    {
+      "type": "WEB",
+      "url": "https://symfony.com/cve-2026-46644"
+    }
+  ],
+  "database_specific": {
+    "cwe_ids": [
+      "CWE-1289"
+    ],
+    "severity": "LOW",
+    "github_reviewed": true,
+    "github_reviewed_at": "2026-05-28T19:52:36Z",
+    "nvd_published_at": null
+  }
+}