Advisory details:
github_osv / GHSA-2xf4-cg6j-vhgq
| Advisory ID | github_osv/GHSA-2xf4-cg6j-vhgq |
| Aliases |
CVE-2026-46644
|
| Summary | symfony/polyfill-intl-idn: xn-- labels with ASCII-only Punycode payloads are treated as equivalent to their decoded form ### Description `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. As 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). Example with `IDNA_USE_STD3_RULES | IDNA_CHECK_BIDI | IDNA_CHECK_CONTEXTJ | IDNA_NONTRANSITIONAL_TO_ASCII`: | Input | Polyfill output | Native `ext-intl` output | | --- | --- | --- | | `poc.xn--kc1zs4-.com` | `poc.kc1zs4.com` | `false` (`errors=1024`) | | `poc.kc1zs4.xn--` | `poc.kc1zs4.` | `false` (`errors=1024`) | Applications using the polyfill to canonicalise or compare hostnames inherit the inconsistency. ### Resolution `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. The patch for this issue is available [here](https://github.com/symfony/polyfill/commit/1be936e2491ccebe152bd736dfc91eb1422c8bec) for branch 1.x. ### Credits Symfony would like to thank Nazy Mad for reporting the issue and Nicolas Grekas for providing the fix. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 2.4 |
| Risk | 1.2 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv4 | 2.7 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-2xf4-cg6j-vhgq/GHSA-2xf4-cg6j-vhgq.json |
| generic_textual | LOW |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
Vector: SSVCv2/E:N/A:Y/T:P/P:M/B:A/M:M/D:T/2026-07-15T12:52:21Z/
Decision: Track
Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/46xxx/CVE-2026-46644.json
Source Advisory: vulnrichment/CVE-2026-46644
[{'Exploitation': 'none'},
{'Automatable': 'yes'},
{'Technical Impact': 'partial'},
{'Mission Prevalence': 'minimal'},
{'Public Well-being Impact': 'material'},
{'Mission & Well-being': 'medium'}]