Summary
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.
Impact
Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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symfony/routing to 5.4.53 or later; symfony/routing to 6.4.41 or later; symfony/routing to 7.4.13 or later; symfony/routing to 8.0.13 or later; symfony/symfony to 5.4.53 or later; symfony/symfony to 6.4.41 or later; symfony/symfony to 7.4.13 or later; symfony/symfony to 8.0.13 or later
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Frequently Asked Questions
- What is CVE-2026-48784? CVE-2026-48784 is a medium-severity open redirect vulnerability in symfony/routing (composer), affecting versions < 5.4.53. It is fixed in 5.4.53, 6.4.41, 7.4.13, 8.0.13. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
- Which packages are affected by CVE-2026-48784?
symfony/routing(composer) (versions < 5.4.53)symfony/symfony(composer) (versions < 5.4.53)
- Is there a fix for CVE-2026-48784? Yes. CVE-2026-48784 is fixed in 5.4.53, 6.4.41, 7.4.13, 8.0.13. Upgrade to this version or later.
- Is CVE-2026-48784 exploitable, and should I be worried? Whether CVE-2026-48784 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-48784 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-48784?
- Upgrade
symfony/routingto 5.4.53 or later - Upgrade
symfony/routingto 6.4.41 or later - Upgrade
symfony/routingto 7.4.13 or later - Upgrade
symfony/routingto 8.0.13 or later - Upgrade
symfony/symfonyto 5.4.53 or later - Upgrade
symfony/symfonyto 6.4.41 or later - Upgrade
symfony/symfonyto 7.4.13 or later - Upgrade
symfony/symfonyto 8.0.13 or later
- Upgrade