Medium severity · published May 26, 2026
CVE-2026-48710
Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks
In wildKEV
6.5
CVSS
70.3%
EPSS
Yes
On KEV
Description
Starlette is a lightweight ASGI framework/toolkit. Prior to version 1.0.1, the HTTP `Host` request header was not validated before being used to reconstruct `request.url`. Because the routing algorithm relies on the raw HTTP path while `request.url` is rebuilt from the `Host` header, a malformed header could make `request.url.path` differ from the path that was actually requested. Middleware and endpoints that apply security restrictions based on `request.url` (rather than the raw `scope` path) could therefore be bypassed. Users should upgrade to a version greater than or equal to version 1.0.1, which validates the `Host` header against the grammar of RFC 9112 §3.2 / RFC 3986 §3.2.2 when constructing `request.url` and falls back to `scope["server"]` for malformed values.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)70.3% · higher than 99% of CVEs
Exploited in the wildYes
CISA KEVListed Sep 2, 2026
Federal remediation dueSep 16, 2026
Ransomware campaign useNot known
Affected products
Which versions
ST
starlette · Kludex
< 1.0.1 · source: vendor, NVD, KEV
AI
AI Inference Server · Redhat
3.3.0 through 3.3.5 · source: NVD
AA
Ansible Automation Platform · Redhat
2.6; 2.7 · source: NVD
EL
Enterprise Linux AI · Redhat
3.0 · source: NVD
MT
Migration Toolkit For Applications · Redhat
before 8.2.0 · source: NVD
OA
Openshift AI · Redhat
3.3 before 3.3.5; 3.4 before 3.4.2 · source: NVD
OL
Openshift Lightspeed · Redhat
All versions, or not specified · source: NVD, CISA
SA
Satellite · Redhat
6.17; 6.18; 6.19 · source: NVD
EI
Exploit Intelligence · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat AI Inference Server · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat AI Inference Server 3.3 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Ansible Automation Platform 2.6 · Red Hat
All versions, or not specified · source: CISA
In the news
AdvisoryHigh
CISA Adds Seven Known Exploited Vulnerabilities to Catalog
CISA has added seven new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog , based on evidence of active exploitation.
CVE-2026-9586 Sangoma Switchvox SQL Injection Vulnerability
CVE-2026-48710 Kludex Starlette HTTP Request/Response Smuggling Vulnerability
CVE-2026-49869 Kestra OSS OS Command Injection Vulnerability
CVE-2026-59822 BerriAI LiteLLM Improper Authentication Vulnerability
CVE-2026-82329 JFrog Artifactory Improper Authentication Vulnerability
CVE-2026-83548 SonicWall SMA1000 Appliances Server-Side Request Forgery Vulnerability
CVE-2026-83549 SonicWall SMA1000 Appliances OS Command Injection Vulnerability
These types of vulnerabilities are a frequent attack vector for malicious cyber actors and pose significant risks to the federal enterprise.
Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities, specifically those identified by Common Vulnerabilities and Exposures (CVEs) listed in CISA’s KEV Catalog on publicly exposed assets that grant total control of the asset post-exploitation, while deferring action f...
Sep 2, 2026·CISA Advisories
VulnerabilityHigh
[CISA KEV] CVE-2026-48710: Kludex Starlette - Kludex Starlette HTTP Request/Response Smuggling Vulnerability
Kludex Starlette contains a HTTP request/response smuggling vulnerability that could allow attackers to inject paths into the host part, prepending the actual path leading to issues such as authentication bypass when the authentication depends on the reconstructed URL’s path. This vulnerability could be chaned with CVE-2026-42271.
STStarletteCVE-2026-48710
Sep 2, 2026·CISA KEV
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-48710
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-48710
CISA KEV catalogue
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
x_refsource_CONFIRM
https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr
x_refsource_MISC
https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6
x_refsource_MISC
https://badhost.org
x_refsource_MISC
https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml
x_refsource_MISC
https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette
x_refsource_MISC
https://www.secwest.net/starlette
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7.5
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5.3
CVE-2026-54282
Starlette: Unvalidated request path concatenated into authority poisons request.url.hostname
5.3
CVE-2026-48817
Starlette: Arbitrary HTTP method dispatched to `HTTPEndpoint` attributes via `getattr`
