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CVE-2026-48710

51
FAUCET Score

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.

First published: May 26, 2026Last modified: May 26, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 0.8.3, < 1.0.1CPE matchmatch criteria
cpe:2.3:a:encode:starlette:*:*:*:*:*:python:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
2.5
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.84%
Probability of exploitation in next 30 days
EPSS Percentile
76.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
Nuclei: CVE-2026-48710 · Jun 2, 2026
This CVE's current EPSS score of 0.0184 is in the 64th percentile among its peer group of 23,701 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: starletteFixed in: 1.0.1

Vendor Advisories (1)

pipGHSA-86qp-5c8j-p5mrmedium

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

Jun 4, 2026

References

access.redhat.com / errata/RHSA-2026:22992
access.redhat.com / errata/RHSA-2026:22993
access.redhat.com / errata/RHSA-2026:23346
access.redhat.com / errata/RHSA-2026:24866
access.redhat.com / errata/RHSA-2026:26226
access.redhat.com / errata/RHSA-2026:30088
access.redhat.com / errata/RHSA-2026:30089
access.redhat.com / errata/RHSA-2026:34456
access.redhat.com / errata/RHSA-2026:34526
access.redhat.com / errata/RHSA-2026:34532
access.redhat.com / errata/RHSA-2026:37275
access.redhat.com / errata/RHSA-2026:43038
access.redhat.com / errata/RHSA-2026:44696
access.redhat.com / security/cve/CVE-2026-48710
bugzilla.redhat.com / show_bug.cgi
security.access.redhat.com / data/csaf/v2/vex/2026/cve-2026-48710.json
badhost.org
MitigationThird Party Advisory
github.com / Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6
Patch
github.com / Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr
Vendor Advisory
github.com / pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml
Third Party Advisory
ostif.org / disclosing-the-badhost-vulnerability-in-starlette
MitigationThird Party Advisory
secwest.net / starlette
ExploitMitigationThird Party Advisory
x41-dsec.de / lab/advisories/x41-2026-002-starlette
ExploitMitigationThird Party Advisory