CVE-2026-121971
Symfony: ScopingHttpClient Sends the Credentials of Its Default Scope to Other Origins Through Network-Path References
Description
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.
INFO
Published Date :
Nov. 4, 2026, 6:17 p.m.
Last Modified :
Nov. 4, 2026, 6:17 p.m.
Remotely Exploit :
Yes !
Source :
596c5446-0ce5-4ba2-aa66-48b3b757a647
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 4.0 | HIGH | 596c5446-0ce5-4ba2-aa66-48b3b757a647 | ||||
| CVSS 4.0 | HIGH | 596c5446-0ce5-4ba2-aa66-48b3b757a647 |
Solution
- Update to Symfony HttpClient 5.4.56 or later.
- Update to Symfony HttpClient 6.4.50 or later.
- Update to Symfony HttpClient 7.4.23 or later.
- Update to Symfony HttpClient 8.1.11 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-121971.
| URL | Resource |
|---|---|
| https://github.com/symfony/symfony/commit/64c34e85bd03b3f8a735d8e1af393659dda91d7c | |
| https://github.com/symfony/symfony/security/advisories/GHSA-gq53-v8w2-gjhj |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-121971 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-121971
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-121971 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-121971 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 596c5446-0ce5-4ba2-aa66-48b3b757a647
Nov. 04, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-200 Added CWE CWE-522 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/121xxx/CVE-2026-121971.json">CVE-2026-121971</a> Added Reference https://github.com/symfony/symfony/commit/64c34e85bd03b3f8a735d8e1af393659dda91d7c Added Reference https://github.com/symfony/symfony/security/advisories/GHSA-gq53-v8w2-gjhj