CVE-2026-27700: X Forwarded For Spoofing

Extracting the first IP address from the 'X-Forwarded-For' header can lead to IP spoofing. Load balancers like AWS ALB append the real client IP to the end of the header, leaving earlier values attacker-controlled. Extracting the first element allows an attacker to spoof their IP address by injecting their own 'X-Forwarded-For' header. Use the last IP addres

Provally CuratedPublic repositoryHighMedium confidenceVerifiedApache-2.0javascript
greprules fetch cve-2026-27700-x-forwarded-for-spoofing --engine opengrep

Description

Extracting the first IP address from the 'X-Forwarded-For' header can lead to IP spoofing. Load balancers like AWS ALB append the real client IP to the end of the header, leaving earlier values attacker-controlled. Extracting the first element allows an attacker to spoof their IP address by injecting their own 'X-Forwarded-For' header. Use the last IP addres

Detection target

Not provided

Recommended fix

Not provided

False-positive notes

Not provided

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