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CVE-2026-46644

symfony/polyfill-intl-idn accepts xn-- labels whose Punycode payload decodes to ASCII-only: insecure equivalence

MEDIUM
6.9
CVSS Score
Published: July 14, 2026 at 08:48 PM UTC
Updated: July 15, 2026 at 06:30 PM UTC
2 products affected across 1 vendorPolyfill Intl IDNPolyfill

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Severity
MEDIUM6.9
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Polyfill· Symfony
60%
v < 1.38.1
Affected range stops below 1.38.1, so it looks safe — our inference, not a vendor statement
Polyfill Intl IDN· Symfony
60%
v < 1.38.1
Affected range stops below 1.38.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (3)

x_refsource_CONFIRM
Source: cverecord
https://github.com/symfony/polyfill/security/advisories/GHSA-2xf4-cg6j-vhgq
x_refsource_MISC
Source: cverecord
https://github.com/symfony/polyfill/commit/1be936e2491ccebe152bd736dfc91eb1422c8bec
x_refsource_MISC
Source: cverecord
https://github.com/symfony/polyfill/releases/tag/v1.38.1

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6.9MEDIUMGitHub_M
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-1289

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