Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained `../` or `./` → Generated URL Collapses Off-Route Under RFC 3986 Normalization
Description
Symfony\Component\Routing\Generator\UrlGenerator::doGenerate() percent-encodes . and .. path segments so that the generated URL still resolves to the originating route after RFC 3986 §5.2.4 dot-segment removal (which strict RFC-3986 consumers — routers, reverse proxies, HTTP clients — perform before percent-decoding).
The encoding was implemented as strtr($url, ['/../' => '/%2E%2E/', '/./' => '/%2E/']) plus a trailing-segment fixup. strtr advances past the trailing / of each match, so the next dot-segment in a chained sequence was left unescaped:
| Input | Output (before fix) | Expected |
|---|---|---|
/../../../ |
/%2E%2E/../%2E%2E/ |
/%2E%2E/%2E%2E/%2E%2E/ |
/foo/../../../bar |
/foo/%2E%2E/../%2E%2E/bar |
/foo/%2E%2E/%2E%2E/%2E%2E/bar |
When a route exposes a parameter constrained by a permissive requirement (.+, .*, or similar) that accepts dots and slashes, attacker-controlled chained .. or . segments produce a generated URL that, under strict RFC 3986 normalization, collapses to a different path than the originating route. The Twig path() / url() helpers and any server-side use of UrlGenerator are affected. Same class of route round-trip integrity issue as CVE-2026-45065.
Note: WHATWG-conformant browsers treat %2E/%2E%2E as dot-segments during URL parsing, so the encoding never protected browser-side traversal. The defense exists for RFC-3986-conformant consumers; restoring it for chained segments closes the gap there.
Resolution
UrlGenerator now matches every /. or /.. dot-segment in a single left-to-right preg_replace_callback pass using a lookahead that does not consume the trailing /, so adjacent dot-segments are encoded correctly.
The patches for this issue are available here for branch 5.4 (and forward-ported to 6.4, 7.4, 8.0 and 8.1).
Credits
Symfony would like to thank Alex Pott for reporting the issue and Nicolas Grekas for providing the fix.
Betroffene Software
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| Plattform | Paket | Anfällige Versionen | Behoben in |
|---|---|---|---|
| Composer-Paket | symfony/routing | < 5.4.53, >= 6.0.0, < 6.4.41, >= 7.0.0, < 7.4.13, >= 8.0.0, < 8.0.13 | 5.4.53, 6.4.41, 7.4.13, 8.0.13 |
| Composer-Paket | symfony/symfony | < 5.4.53, >= 6.0.0, < 6.4.41, >= 7.0.0, < 7.4.13, >= 8.0.0, < 8.0.13 | 5.4.53, 6.4.41, 7.4.13, 8.0.13 |
Verweise
- https://github.com/symfony/symfony/security/advisories/GHSA-h5x3-xfc9-m39h
- https://github.com/symfony/symfony/commit/4b63c3a3f7af04ecd79c89a594b0b02a01990b1d
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/routing/CVE-2026-48784.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-48784.yaml
- https://github.com/symfony/symfony
- https://symfony.com/cve-2026-48784
- CVSS-Vektor
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N- Schwäche (CWE)
CWE-172, CWE-601- Plattform
- Composer
- Paket
symfony/routing, symfony/symfony- Veröffentlicht
- 15.06.2026
- Aktualisiert
- 11.10.2026 10:22
Quellen und Lizenzen
OSV / GitHub Advisory Database - GHSA-h5x3-xfc9-m39h - CC BY 4.0
Schwachstellenhistorie: symfony/symfony
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- 100
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- 11.2019 06.2026
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Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained `../` or `./` → Generated URL Collapses Off-Route Under RFC 3986 Normalization dieser Eintrag
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