CVE-2026-48710
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
OS impact
SUSE Affected 1 release
| Version | Status | Fixed in |
|---|---|---|
| — | Affected | — |
Debian Mixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 0.46.1-3+deb13u2 |
| sid | Fixed | 1.1.0-1 |
| forky | Fixed | 1.1.0-1 |
| bullseye | Affected | — |
| bookworm | Fixed | 0.26.1-1+deb12u1 |
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| PyPI | starlette | <1.0.1 | 1.0.1 |
Application impact
| Vendor | Product | Versions | Fixed |
|---|---|---|---|
| encode | starlette | {"startIncluding":"0.8.3","endExcluding":"1.0.1"} | 1.0.1 |
References
- https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr
- https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6
- https://badhost.org
- https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml
- https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette
- https://www.secwest.net/starlette
- https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette
- https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette/
- https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette/
- https://www.suse.com/security/cve/CVE-2026-48710.html
- https://security-tracker.debian.org/tracker/CVE-2026-48710
CWEs
CWE-444
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.