Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained ../ or ./ → Generated URL Collapses Off-Route Under RFC 3986 Normalization

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · 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 · score source

EPSS

• CVE-2026-48784: 0.35% estimated exploitation activity in the next 30 days; percentile 28.50 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

15 Jun 2026, 17:33 UTC

Last modified by the source

15 Jun 2026, 17:33 UTC

Source last checked

26 Oct 2026, 14:49 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-h5x3-xfc9-m39h

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# Patch Next advisory brief: CVE-2026-48784

Advisory: Symfony: UrlGenerator Dot-Segment Encoding Skips Every Other Chained `../` or `./` → Generated URL Collapses Off-Route Under RFC 3986 Normalization
IDs: CVE-2026-48784, GHSA-h5x3-xfc9-m39h
Record: https://patchnext.com/advisories/cve-2026-48784 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: symfony/symfony 8.0.13, 7.4.13, 6.4.41, 5.4.53; symfony/routing 8.0.13, 7.4.13, 6.4.41, 5.4.53. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist symfony/symfony: affected < 5.4.53; >= 6.0.0, < 6.4.41; >= 7.0.0, < 7.4.13; >= 8.0.0, < 8.0.13; fixed in 6.4.41, 8.0.13, 7.4.13, 5.4.53
- Packagist symfony/routing: affected < 5.4.53; >= 6.0.0, < 6.4.41; >= 7.0.0, < 7.4.13; >= 8.0.0, < 8.0.13; fixed in 6.4.41, 8.0.13, 7.4.13, 5.4.53

## Suggested inspection (read-only)
- Packagist symfony/symfony: check the installed version with your package manager.
- Packagist symfony/routing: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on symfony/symfony, symfony/routing.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-h5x3-xfc9-m39h (GitHub-reviewed advisory GHSA-h5x3-xfc9-m39h lists affected ranges: Packagist symfony/routing >=0 =6.0.0 =7.0.0 =8.0.0 =0 =6.0.0 =7.0.0 =8.0.0 <8.0.13)

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