LiveActive security incident?Get immediate response
CVE Record

CVE-2026-48710: Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks

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.

MediumCVSS 6.5Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This issue affects Starlette before 1.0.1. A malformed Host header could make the application believe a different URL path was requested than the one actually routed. If an application made security decisions from request.url, path-based protections could be bypassed.

Executive priority

Treat as a moderate-priority dependency update. It is not reported as actively exploited, but it can undermine path-based security controls in affected Starlette services. Prioritize internet-facing services and apps with custom middleware.

Technical view

Starlette reconstructed request.url from the Host header without validating that header first. Routing used the raw ASGI path, but request.url.path could differ. Code that enforced authorization or restrictions using request.url rather than the raw scope path could apply checks to the wrong path.

Likely exposure

Exposure is most likely in Starlette applications below 1.0.1 where middleware or endpoints use request.url for path-based authorization, filtering, redirects, or access controls. Applications that rely only on router matching or raw scope path are less clearly exposed.

Exploitation context

The source bundle marks this as not in KEV and provides no evidence of active exploitation. The issue is network-reachable, unauthenticated, and low complexity, but impact depends on application-specific security logic using request.url.path.

Researcher notes

Focus triage on the trust boundary between ASGI scope path, Host parsing, and request.url consumers. The central question is whether security logic reads reconstructed URL path data rather than the route path actually matched by Starlette.

Mitigation direction

  • Upgrade Starlette to version 1.0.1 or later.
  • Audit middleware and endpoints that make security decisions from request.url.
  • Prefer raw routed path or validated framework primitives for access checks.
  • Review Red Hat or platform vendor advisories for packaged deployments.
  • Add regression tests for malformed Host handling around protected paths.

Validation and detection

  • Inventory deployed Starlette versions and flag anything below 1.0.1.
  • Search application code for request.url use in authorization or filtering.
  • Confirm dependency lockfiles resolve Starlette 1.0.1 or later.
  • Review tests covering protected routes and Host header parsing behavior.
  • Check vendor VEX or errata status for managed distributions.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-1289: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cwe · low confidence lookup

CWE-444: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-48710 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.5 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
22Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
6.5CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N3.92.5GitHub_M
6.5CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N3.92.5redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

6.5Medium
CVSS 3.1 vector shape for CVE-2026-48710Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPstarlette: Starlette: Security restriction bypass via malformed HTTP Host header
other:Red Hat severity ratingcvssV3_1
  • 2026-05-26T23:01:03.204Z: Reported to Red Hat.
  • 2026-05-26T21:54:54.393Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Kludexstarlette< 1.0.1Listed
Weakness

CWE details

CWE-1289CWE-444

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.