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Starlette CVE-2026-48710

| EUVDEUVD-2026-32016 MEDIUM
HTTP Request/Response Smuggling (CWE-444)
2026-05-26 security-advisories@github.com GHSA-86qp-5c8j-p5mr PYSEC-2026-161
Medium
Disputed · 6.5 NVD
View

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V4 - API and Web Service HTTP request consistency
Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.
Exploited in the wild (CISA KEV) Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – May 26, 2026

Host header injection in Starlette prior to version 1.0.1 allows unauthenticated remote attackers to cause request.url.path to differ from the actual ASGI scope path used for routing, enabling bypass of middleware and endpoint security controls that rely on request.url rather than the raw scope. Any application enforcing path-based ACLs, authentication gates, or WAF-style filters through request.url is affected, as a crafted Host header can make the URL appear to address a permitted path while the real route differs. This issue carries CVSS 6.5 (AV:N/AC:L/PR:N/UI:N); no public exploit has been identified at time of analysis and it is not listed in CISA KEV.

Affected VersionsENISA

starlette < 1.0.1

Affected Packages

pypi starlette fix: 1.0.1

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in pypi

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Sources disagree (Medium–Critical)
NVD PRIMARY 6.5 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
SUSE MEDIUM
Red Hat 6.5 CRITICAL

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

1
Added to CISA KEV
Sep 02, 2026 - 17:02 CISA

DescriptionNVD

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.

Threat Intelligence Overview

Threat Score
4.3/10
Composite threat intelligence
EPSS Score
0.0%
Top 90% exploitable
Threat Intel
1
1 sources
Exploit
POC
Public exploit code exists
Social Media
7
Sightings
Data Quality
9 sources
Confidence: High

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV Yes
Public POC Yes
EPSS 0.0%
Patch available Yes
Active threat Yes
Deciding rule
In CISA KEV with patch available
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
High
Technical Impact
Partial

Priority Score

102
Low Medium High Critical
KEV: +50
EPSS: 0
CVSS: +32
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

HTTP request smuggling exploits inconsistencies in how front-end and back-end servers parse HTTP message boundaries.

Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Server 16.0 Fixed
SUSE Linux Enterprise Server 16.1 Fixed
SUSE Linux Enterprise Server for SAP applications 16.0 Fixed
SUSE Linux Enterprise Server for SAP applications 16.1 Fixed
openSUSE Leap 16.0 Fixed

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-48710 ADVISORY https://vuldb.com/vuln/365870 REF https://access.redhat.com/errata/RHSA-2026:22992 REF https://access.redhat.com/errata/RHSA-2026:22993 REF https://access.redhat.com/errata/RHSA-2026:23346 REF https://access.redhat.com/errata/RHSA-2026:24866 REF https://access.redhat.com/errata/RHSA-2026:26226 REF https://access.redhat.com/errata/RHSA-2026:30088 REF https://access.redhat.com/errata/RHSA-2026:30089 REF https://access.redhat.com/errata/RHSA-2026:34456 REF https://access.redhat.com/errata/RHSA-2026:34526 REF https://access.redhat.com/errata/RHSA-2026:34532 REF https://access.redhat.com/errata/RHSA-2026:37275 REF https://access.redhat.com/errata/RHSA-2026:43038 REF https://access.redhat.com/errata/RHSA-2026:44696 REF https://access.redhat.com/errata/RHSA-2026:51357 REF https://access.redhat.com/errata/RHSA-2026:60520 REF https://access.redhat.com/errata/RHSA-2026:63337 REF https://access.redhat.com/security/cve/CVE-2026-48710 REF https://badhost.org REF https://bugzilla.redhat.com/show_bug.cgi?id=2481742 REF https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6 REF https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr REF https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml REF https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette REF https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48710.json REF https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48710 REF https://www.cve.org/CVERecord?id=CVE-2026-48710 REF https://www.secwest.net/starlette REF https://www.wiz.io/blog/ai-infrastructure-honeypot REF https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette REF https:/www.microsoft.com/en-us/security/blog/2026/08/26/when-ai-infrastructure-becomes-target-securing-gateways-control-points

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