CVE-2026-48710

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

CVSS 3.1 Medium 6.5Known exploited (CISA KEV)

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

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.

Key data

CVSS 3.1 Medium 6.5

Score published by GitHub_M in the CVE record.

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

Attack vector: Network
The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity: Low
No special conditions are needed. The attack can be repeated at will.
Privileges required: None
No account or privileges are needed.
User interaction: None
No action from any user is needed.
Scope: Unchanged
The impact stays within the vulnerable component.
Confidentiality impact: Low
Limited effect on the secrecy of data.
Integrity impact: Low
Limited effect on the trustworthiness of data.
Availability impact: None
No effect on availability.

Metric	Value	What it means
Attack vector	Network	The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity	Low	No special conditions are needed. The attack can be repeated at will.
Privileges required	None	No account or privileges are needed.
User interaction	None	No action from any user is needed.
Scope	Unchanged	The impact stays within the vulnerable component.
Confidentiality impact	Low	Limited effect on the secrecy of data.
Integrity impact	Low	Limited effect on the trustworthiness of data.
Availability impact	None	No effect on availability.

CVSS 3.1 Medium 6.5

Score published by redhat-SADP in the CVE record.

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

Attack vector: Network
The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity: Low
No special conditions are needed. The attack can be repeated at will.
Privileges required: None
No account or privileges are needed.
User interaction: None
No action from any user is needed.
Scope: Unchanged
The impact stays within the vulnerable component.
Confidentiality impact: Low
Limited effect on the secrecy of data.
Integrity impact: Low
Limited effect on the trustworthiness of data.
Availability impact: None
No effect on availability.

Metric	Value	What it means
Attack vector	Network	The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity	Low	No special conditions are needed. The attack can be repeated at will.
Privileges required	None	No account or privileges are needed.
User interaction	None	No action from any user is needed.
Scope	Unchanged	The impact stays within the vulnerable component.
Confidentiality impact	Low	Limited effect on the secrecy of data.
Integrity impact	Low	Limited effect on the trustworthiness of data.
Availability impact	None	No effect on availability.

CVSS is owned and managed by FIRST.Org, Inc. (FIRST) and is used by permission. Each CVSS score on this site is shown together with its vector string, as published in the CVE record by the source named next to it. Learn more at first.org/cvss.

EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score: 0.70288 (70.3% probability)
Percentile: 99.4%
Scores of: Nov 10, 2026
Model: v2026.06.15

CISA Known Exploited Vulnerabilities

This CVE is listed in the CISA KEV catalog.

Name in the catalog: Kludex Starlette HTTP Request/Response Smuggling Vulnerability
Added to the catalog: Sep 2, 2026
Federal due date: Sep 16, 2026

CISA assessment as of Sep 3, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.

Exploitation: Recorded by CISA as active
Automatable: yes
Technical impact: partial

Weakness (CWE)

CWE catalog version 5.0.

CWE-444Inconsistent Interpretation of HTTP Requests
CWE-1289Improper Validation of Unsafe Equivalence in Input

Affected products

Products listed in the CVE record, as the CNA published them.

Kludex starlette
- affected: < 1.0.1

References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

github.comx_refsource_CONFIRM
github.comx_refsource_MISC
badhost.orgx_refsource_MISC
github.comx_refsource_MISC
ostif.orgx_refsource_MISC
secwest.netx_refsource_MISC
x41-dsec.dex_refsource_MISC

Timeline

ID reservedMay 22, 2026
Record publishedMay 26, 2026
Added to CISA KEVSep 2, 2026
Record last updatedOct 1, 2026

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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:07 UTC. Sources and licenses