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Prebid ServerApplication · Prebid

CVE-2026-54735

CRITICAL · 10.0 CVSS v3.1 Published 2026-07-29
Fix available
A fix is available. Upgrade to 4.4.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click 3 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Prebid Server prior to v4.4.0 contains a Server-Side Request Forgery (SSRF) vulnerability where certain bidder adapters interpolate user-supplied parameters into outbound HTTP request URLs without validating host and subdomain values. Attackers can craft bid request parameters to redirect requests to internal network services or sensitive endpoints, potentially exposing internal infrastructure.

MitigationUpgrade Prebid Server to version 4.4.0 or later. Additionally, implement strict allowlist validation for host and subdomain parameters in all bidder adapters to prevent requests to internal/private IP ranges and untrusted domains.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Prebid ServerApplication
Affected:< 4.4.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine Prebid Server version
    Check the running Prebid Server binary or container image tag for the version number. Common ways include: running 'prebid-server --version', checking the Docker image tag, or reviewing the build artifacts. Compare the version to v4.4.0 - versions prior to v4.4.0 are affected.
    Affected if The installed version is earlier than v4.4.0
  2. Identify active bidder adapters
    Review the Prebid Server configuration files (often in config/ or yaml format) to identify which bidder adapters are enabled. Bidders are typically defined in the 'adapters' or 'bidders' section of the configuration.
    Affected if Any bidder adapters are configured and active - the vulnerability exists in how adapters handle user-supplied parameters in bid requests
  3. Verify network egress configuration
    Inspect the Prebid Server network settings to determine if the server is permitted to make outbound HTTP requests. Check for firewall rules, network policies, or proxy configuration that control outbound connections from the Prebid Server host.
    Affected if The server has unrestricted or broad outbound network access, allowing potential SSRF targets to be reached
  4. Review bidder endpoint configuration
    Examine the bidder adapter endpoint configurations to see if URLs accept user-supplied parameters (common in 'usersync', 'endpoint', or 'url' settings). Look for patterns where bid request fields are interpolated into HTTP URLs.
    Affected if Bidder adapters are configured to pass-through or interpolate request parameters into outbound request URLs without host validation

You are affected if running Prebid Server version earlier than v4.4.0 with bidder adapters enabled and any outbound network access capability.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.4.0 or later
Fixed in 4.4.0
Interim mitigation

Upgrade Prebid Server to version 4.4.0 or later. Additionally, implement strict allowlist validation for host and subdomain parameters in all bidder adapters to prevent requests to internal/private IP ranges and untrusted domains.

Recommended fix High confidence

Prebid Server version 4.4.0

  1. Identify the current Prebid Server version running in your environment
  2. Review the Prebid Server 4.4.0 release notes for any configuration or behavioral changes
  3. Back up your Prebid Server configuration and any custom bidder adapter configurations
  4. Upgrade Prebid Server to version 4.4.0 or later
  5. Verify the upgrade was successful by checking the server version
  6. Test that legitimate bid requests still function correctly with your configured bidders
Caveat Review 4.4.0 release notes for any breaking changes to bidder adapter behavior or configuration requirements

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Prebid Server Scoped from the published advisory
  • Consultation4.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-54735 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data