Bug 2567520 (CVE-2026-121971) - CVE-2026-121971 symfony/http-client: symfony/http-client: Information disclosure via relative URL handling
Summary: CVE-2026-121971 symfony/http-client: symfony/http-client: Information disclos...
Keywords:
Status: NEW
Alias: CVE-2026-121971
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
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Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-11-05 22:04 UTC by OSIDB Bzimport
Modified: 2026-11-05 22:53 UTC (History)
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Description OSIDB Bzimport 2026-11-05 22:04:29 UTC
The component ScopingHttpClient in Symfony HttpClient merges the options of its default scope (such as auth_bearer or auth_basic) into a request before resolving a relative URL against the base_uri, allowing a network-path reference such as "//evil.example/steal" to be sent to another origin together with the default scope’s credentials, and resulting in potential disclosure of those credentials to an attacker-controlled server. This affects Symfony in versions 5.x prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.



The resolved URL falls outside the origin of the base URI, yet it keeps the merged options, whereas the absolute spelling "https://evil.example/steal" receives none. The same happens with a different port or user-info part on the same host.









This is reachable whenever an attacker controls the beginning of a URL passed to a client built with a base_uri and credentials, including those created with HttpClient::createForBaseUri() or configured under framework.http_client.scoped_clients.

To solve the issue, after resolving a relative URL against the base URI of the default scope, ScopingHttpClient now compares the scheme and authority of the result with those of the base URI, parsed the way the request is sent.


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