Authentication bypass via matching forged IP headers
Published Jan 30, 2026 · Updated Jan 30, 2026
Authentication bypass in Rogério Zambon's http-protection 0.2.0 and earlier allows remote attackers to evade IP spoofing checks. The IpSpoofing middleware trusts attacker-controlled X-Forwarded-For values and only rejects X-Client-IP or X-Real-IP values absent from that list. Unauthenticated network requests pass the middleware when all three headers carry the same forged address, allowing access only where an application relies on this check.
Summary
What happened
Authentication bypass in Rogério Zambon's http-protection 0.2.0 and earlier allows remote attackers to evade IP spoofing checks. The IpSpoofing middleware trusts attacker-controlled X-Forwarded-For values and only rejects X-Client-IP or X-Real-IP values absent from that list. Unauthenticated network requests pass the middleware when all three headers carry the same forged address, allowing access only where an application relies on this check.
The record
- CVE
- CVE-2020-37056
- Published
- Jan 30, 2026
- Updated
- Jan 30, 2026
- Vendor
- Rogério Zambon
- Product
- http-protection
- Classifications
- CWE-290, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 30, 2026CVE publishedPublication date reported by the CVE source.
- Jan 30, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=<= 0.2.0
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Crystal Shard http-protection 0.2.0 - IP Spoofing Bypassproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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