CVE-2026-48710

Public on

Last Modified: UTC

Critical Critical Impact What does this mean?
6.5 CVSS v3 Base Score

Description

A flaw was found in Starlette, a lightweight ASGI (Asynchronous Server Gateway Interface) framework. A remote attacker could exploit this vulnerability by sending a specially crafted HTTP Host request header. This malformed header could cause the request.url to be incorrectly reconstructed, leading to a discrepancy with the actual requested path. Consequently, security restrictions enforced by middleware and endpoints that rely on request.url for validation could be bypassed, potentially allowing unauthorized access or actions.

Statement

The impact is rated as Critical because path-based authentication and access control middleware can be completely bypassed by an unauthenticated remote attacker using a crafted HTTP Host header.

Starlette reconstructs request.url by combining the HTTP Host header value with the request path, but performs no validation on the Host header. An attacker can inject path separators or query characters into the Host header (e.g., Host: example.com/health?x=), causing request.url.path to return a value that differs from the actual HTTP request path used for routing. Middleware that enforces authentication or authorization decisions based on request.url.path will evaluate the injected path rather than the real one, allowing the attacker to reach protected endpoints.

With regard to CVSS metrics, the Attack Vector (AV) is Network and Privileges Required (PR) is None, because the attack requires only the ability to send HTTP requests with a crafted Host header. User interaction is not required.

Red Hat Satellite / Insights (IoP): The starlette package is included as a dependency of Connexion, but this flaw is rated Low impact because these services do not use path-based authentication middleware and all services are deployed behind reverse proxies.

OpenShift Lightspeed (OLS): The starlette package is included as a dependency, but this flaw is rated Low impact because authentication is enforced via Kubernetes TokenReview/SubjectAccessReview through FastAPI dependency injection, not path-based middleware; request.url.path is only used for metrics and response header application.

RHOAI Kubeflow Training images: starlette is being used as indirect dependency of mlflow, but this flaw is rated as Low impact because mlflow is used as client library only to store training metrics on remote server, it doesn't expose any endpoint.

RHOAI odh-automl: The impact is reduced to Low since starlette is only used in the backend and it's transient dependency and starlette is not used at all to serve any endpoints.

RHOAI odh-kserve-autogluon-server-rhel9: While the Starlette dependency is present in the build, the vulnerable code in starlette is not reachable. This reduces the impact to low.

Mitigation

Deploying an RFC-compliant reverse proxy (such as nginx, Apache, HAProxy, or Caddy) in front of the ASGI server will reject malformed Host headers before they reach the application. This is the most straightforward mitigation that does not require code changes.

If custom middleware is present, it should be updated to use `request.scope["path"]` instead of `request.url.path` for any security decisions. The ASGI scope path is derived from the HTTP request line and is not influenced by the Host header, so it reflects the actual request target.

Additional Information

External References

Content from www.cve.org is not included.https://www.cve.org/CVERecord?id=CVE-2026-48710

Content from nvd.nist.gov is not included.https://nvd.nist.gov/vuln/detail/CVE-2026-48710

Content from badhost.org is not included.https://badhost.org

Content from github.com is not included.https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6

Content from github.com is not included.https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr

Content from github.com is not included.https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml

Content from ostif.org is not included.https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette

Content from www.secwest.net is not included.https://www.secwest.net/starlette

Content from www.x41-dsec.de is not included.https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette

Affected Packages and Issued Red Hat Security Errata

Products / Services Components State Errata
Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9 Affected
Migration Toolkit for Applications 8 mta/mta-solution-server-rhel9 Affected
OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9 Affected
OpenShift Lightspeed openshift-lightspeed/lightspeed-service-api-rhel9 Affected
Red Hat AI Inference Server rhaii/vllm-cpu-rhel9 Affected
Red Hat AI Inference Server rhaii/vllm-cuda-rhel9 Affected
Red Hat AI Inference Server rhaii/vllm-rocm-rhel9 Affected
Red Hat AI Inference Server rhaii/vllm-spyre-rhel9 Affected
Red Hat AI Inference Server rhaiis/vllm-cuda-rhel9 Affected
Red Hat AI Inference Server rhaiis/vllm-rocm-rhel9 Affected
Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown Red Hat NVD
CVSS v3 Base Score 6.5 6.5
Attack Vector Network Network
Attack Complexity Low Low
Privileges Required None None
User Interaction None None
Scope Unchanged Unchanged
Confidentiality Impact Low Low
Integrity Impact Low Low
Availability Impact None None

CVSS v3 Vector

Red Hat CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

NVD CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.

My product is listed as "Out of Support Scope". What does this mean?

 When a product is listed as "Out of Support Scope", it means a vulnerability with the impact level assigned to this CVE is no longer covered by its current support lifecycle phase. The product has been identified to contain the impacted component, but analysis to determine whether it is affected or not by this vulnerability was not performed. The product should be assumed to be affected. Customers are advised to apply any mitigation options documented on this page, consider removing or disabling the impacted component, or upgrade to a supported version of the product that has an update available.