Vulnerability-Lookup

CVE-2026-45045 (GCVE-0-2026-45045)

Vulnerability from cvelistv5 – Published: 2026-07-08 19:26 – Updated: 2026-07-09 13:20

Title

Fiber: X-Real-IP Spoofing via Header.Add() in BalancerForward

Summary

Fiber is an Express inspired web framework written in Go. Prior to 3.3.0 and 2.52.14, the BalancerForward proxy helper in middleware/proxy/proxy.go uses Header.Add() instead of Header.Set() when injecting X-Real-IP, allowing an attacker-supplied first X-Real-IP value to be forwarded to upstream servers for logging, rate limiting, and access control. This issue is fixed in version 3.3.0 and 2.52.14.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-09 13:19 UTC

CWE

CWE-290 - Authentication Bypass by Spoofing

Assigner

GitHub_M mitre root

References

7 references

URL	Tags
https://github.com/gofiber/fiber/security/advisor…	x_refsource_CONFIRM
https://github.com/gofiber/fiber/pull/4260	x_refsource_MISC
https://github.com/gofiber/fiber/pull/4495	x_refsource_MISC
https://github.com/gofiber/fiber/commit/1403cc829…	x_refsource_MISC
https://github.com/gofiber/fiber/commit/33c950128…	x_refsource_MISC
https://github.com/gofiber/fiber/releases/tag/v2.52.14	x_refsource_MISC
https://github.com/gofiber/fiber/releases/tag/v3.3.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
gofiber	fiber	Affected: >= 3.0.0-beta.2, < 3.3.0 Affected: < 2.52.14	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-45045",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-09T13:19:42.395861Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-09T13:20:08.367Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "fiber",
          "vendor": "gofiber",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.0.0-beta.2, \u003c 3.3.0"
            },
            {
              "status": "affected",
              "version": "\u003c 2.52.14"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Fiber is an Express inspired web framework written in Go. Prior to 3.3.0 and 2.52.14, the BalancerForward proxy helper in middleware/proxy/proxy.go uses Header.Add() instead of Header.Set() when injecting X-Real-IP, allowing an attacker-supplied first X-Real-IP value to be forwarded to upstream servers for logging, rate limiting, and access control. This issue is fixed in version 3.3.0 and 2.52.14."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-290",
              "description": "CWE-290: Authentication Bypass by Spoofing",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-08T19:26:26.580Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876"
        },
        {
          "name": "https://github.com/gofiber/fiber/pull/4260",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gofiber/fiber/pull/4260"
        },
        {
          "name": "https://github.com/gofiber/fiber/pull/4495",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gofiber/fiber/pull/4495"
        },
        {
          "name": "https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396"
        },
        {
          "name": "https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d"
        },
        {
          "name": "https://github.com/gofiber/fiber/releases/tag/v2.52.14",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gofiber/fiber/releases/tag/v2.52.14"
        },
        {
          "name": "https://github.com/gofiber/fiber/releases/tag/v3.3.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/gofiber/fiber/releases/tag/v3.3.0"
        }
      ],
      "source": {
        "advisory": "GHSA-gcfq-8gqf-4876",
        "discovery": "UNKNOWN"
      },
      "title": "Fiber: X-Real-IP Spoofing via Header.Add() in BalancerForward"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-45045",
    "datePublished": "2026-07-08T19:26:26.580Z",
    "dateReserved": "2026-05-08T18:07:27.341Z",
    "dateUpdated": "2026-07-09T13:20:08.367Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-45045",
      "date": "2026-09-16",
      "epss": "0.00463",
      "percentile": "0.3911"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-45045\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-07-08T20:16:50.060\",\"lastModified\":\"2026-07-15T20:50:55.160\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Fiber is an Express inspired web framework written in Go. Prior to 3.3.0 and 2.52.14, the BalancerForward proxy helper in middleware/proxy/proxy.go uses Header.Add() instead of Header.Set() when injecting X-Real-IP, allowing an attacker-supplied first X-Real-IP value to be forwarded to upstream servers for logging, rate limiting, and access control. This issue is fixed in version 3.3.0 and 2.52.14.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"gofiber\",\"product\":\"fiber\",\"versions\":[{\"version\":\"\u003e= 3.0.0-beta.2, \u003c 3.3.0\",\"status\":\"affected\"},{\"version\":\"\u003c 2.52.14\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-07-09T13:19:42.395861Z\",\"id\":\"CVE-2026-45045\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-290\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:gofiber:fiber:*:*:*:*:*:go:*:*\",\"versionEndExcluding\":\"2.52.14\",\"matchCriteriaId\":\"34B804BA-609E-4B3E-80E0-D1D3EC25E3F0\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:gofiber:fiber:*:*:*:*:*:go:*:*\",\"versionStartIncluding\":\"3.0.0\",\"versionEndExcluding\":\"3.3.0\",\"matchCriteriaId\":\"A091E1AB-E012-47CA-9674-734334483EF0\"}]}]}],\"references\":[{\"url\":\"https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/gofiber/fiber/pull/4260\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Issue Tracking\",\"Patch\"]},{\"url\":\"https://github.com/gofiber/fiber/pull/4495\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Issue Tracking\",\"Patch\"]},{\"url\":\"https://github.com/gofiber/fiber/releases/tag/v2.52.14\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Release Notes\"]},{\"url\":\"https://github.com/gofiber/fiber/releases/tag/v3.3.0\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Release Notes\"]},{\"url\":\"https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Exploit\",\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "current_release_date": "2026-08-24T12:18:43+00:00",
      "cve": "CVE-2026-45045",
      "id": "CVE-2026-45045",
      "initial_release_date": "2026-07-08T19:26:26.580000+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "github.com/gofiber/fiber: GoFiber: IP spoofing allows bypass of security controls via X-Real-IP header manipulation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45045.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-11T00:06:55Z",
      "cve": "CVE-2026-45045",
      "id": "CVE-2026-45045",
      "initial_release_date": "2026-08-11T00:06:55Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-45045",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-45045.json",
      "version": "2"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-45045\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-07-09T13:19:42.395861Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-07-09T13:19:46.171Z\"}}], \"cna\": {\"title\": \"Fiber: X-Real-IP Spoofing via Header.Add() in BalancerForward\", \"source\": {\"advisory\": \"GHSA-gcfq-8gqf-4876\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 5.3, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N\", \"integrityImpact\": \"LOW\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}}], \"affected\": [{\"vendor\": \"gofiber\", \"product\": \"fiber\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003e= 3.0.0-beta.2, \u003c 3.3.0\"}, {\"status\": \"affected\", \"version\": \"\u003c 2.52.14\"}]}], \"references\": [{\"url\": \"https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876\", \"name\": \"https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/gofiber/fiber/pull/4260\", \"name\": \"https://github.com/gofiber/fiber/pull/4260\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/gofiber/fiber/pull/4495\", \"name\": \"https://github.com/gofiber/fiber/pull/4495\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396\", \"name\": \"https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d\", \"name\": \"https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/gofiber/fiber/releases/tag/v2.52.14\", \"name\": \"https://github.com/gofiber/fiber/releases/tag/v2.52.14\", \"tags\": [\"x_refsource_MISC\"]}, {\"url\": \"https://github.com/gofiber/fiber/releases/tag/v3.3.0\", \"name\": \"https://github.com/gofiber/fiber/releases/tag/v3.3.0\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Fiber is an Express inspired web framework written in Go. Prior to 3.3.0 and 2.52.14, the BalancerForward proxy helper in middleware/proxy/proxy.go uses Header.Add() instead of Header.Set() when injecting X-Real-IP, allowing an attacker-supplied first X-Real-IP value to be forwarded to upstream servers for logging, rate limiting, and access control. This issue is fixed in version 3.3.0 and 2.52.14.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-290\", \"description\": \"CWE-290: Authentication Bypass by Spoofing\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-07-08T19:26:26.580Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-45045\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-09T13:20:08.367Z\", \"dateReserved\": \"2026-05-08T18:07:27.341Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-07-08T19:26:26.580Z\", \"assignerShortName\": \"GitHub_M\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

FKIE_CVE-2026-45045

Vulnerability from fkie_nvd - Published: 2026-07-08 20:16 - Updated: 2026-07-15 20:50

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396	Patch
security-advisories@github.com	https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d	Patch
security-advisories@github.com	https://github.com/gofiber/fiber/pull/4260	Issue Tracking, Patch
security-advisories@github.com	https://github.com/gofiber/fiber/pull/4495	Issue Tracking, Patch
security-advisories@github.com	https://github.com/gofiber/fiber/releases/tag/v2.52.14	Release Notes
security-advisories@github.com	https://github.com/gofiber/fiber/releases/tag/v3.3.0	Release Notes
security-advisories@github.com	https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	gofiber	fiber	*
	gofiber	fiber	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "fiber",
          "vendor": "gofiber",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.0.0-beta.2, \u003c 3.3.0"
            },
            {
              "status": "affected",
              "version": "\u003c 2.52.14"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:gofiber:fiber:*:*:*:*:*:go:*:*",
              "matchCriteriaId": "34B804BA-609E-4B3E-80E0-D1D3EC25E3F0",
              "versionEndExcluding": "2.52.14",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:gofiber:fiber:*:*:*:*:*:go:*:*",
              "matchCriteriaId": "A091E1AB-E012-47CA-9674-734334483EF0",
              "versionEndExcluding": "3.3.0",
              "versionStartIncluding": "3.0.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Fiber is an Express inspired web framework written in Go. Prior to 3.3.0 and 2.52.14, the BalancerForward proxy helper in middleware/proxy/proxy.go uses Header.Add() instead of Header.Set() when injecting X-Real-IP, allowing an attacker-supplied first X-Real-IP value to be forwarded to upstream servers for logging, rate limiting, and access control. This issue is fixed in version 3.3.0 and 2.52.14."
    }
  ],
  "id": "CVE-2026-45045",
  "lastModified": "2026-07-15T20:50:55.160",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-45045",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-09T13:19:42.395861Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-08T20:16:50.060",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Issue Tracking",
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/pull/4260"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Issue Tracking",
        "Patch"
      ],
      "url": "https://github.com/gofiber/fiber/pull/4495"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/gofiber/fiber/releases/tag/v2.52.14"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/gofiber/fiber/releases/tag/v3.3.0"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-290"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-GCFQ-8GQF-4876

Vulnerability from github – Published: 2026-07-02 13:50 – Updated: 2026-08-04 21:52

Summary

GoFiber Vulnerable to X-Real-IP Spoofing via Header.Add() in BalancerForward

Details

Summary

The BalancerForward proxy helper in GoFiber uses Header.Add() instead of Header.Set() when injecting the X-Real-IP header. This appends the real client IP as a second header value rather than replacing any attacker-supplied value. Upstream servers that read the first X-Real-IP header (nginx, Express, most HTTP servers) use the attacker's spoofed IP for logging, rate limiting, and access control.

Vulnerable Code

File: middleware/proxy/proxy.go, lines 270-285

func BalancerForward(servers []string, clients ...*fasthttp.Client) fiber.Handler {
    r := &roundrobin{
        current: 0,
        pool:    servers,
    }
    return func(c fiber.Ctx) error {
        server := r.get()
        if !strings.HasPrefix(server, "http") {
            server = "http://" + server
        }
        c.Request().Header.Add("X-Real-IP", c.IP())   // line 282: Add, not Set
        return Do(c, server+c.OriginalURL(), clients...)
    }
}

Data Flow

Attacker sends request with X-Real-IP: 10.0.0.1 (spoofed internal IP)
BalancerForward handler executes at line 282
c.Request().Header.Add("X-Real-IP", c.IP()) APPENDS the real IP as a second header
Upstream server receives: X-Real-IP: 10.0.0.1 AND X-Real-IP: <real-attacker-ip>
Most HTTP servers (nginx, Node.js, Apache) read the FIRST value
Upstream uses 10.0.0.1 for all IP-dependent logic

Impact

Rate limit bypass: IP-based rate limiting at the upstream uses the spoofed IP, allowing unlimited requests
IP ACL bypass: Internal IP allowlists (e.g., admin panels restricted to 10.0.0.0/8) can be bypassed
Audit log poisoning: Security logs record the spoofed IP, making incident investigation unreliable
Geolocation bypass: IP-based geofencing or region restrictions are circumvented

Fix

Replace Header.Add() with Header.Set() at line 282:

c.Request().Header.Set("X-Real-IP", c.IP())

Header.Set() replaces any existing header value, ensuring only the real client IP is forwarded.

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.2.0"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/gofiber/fiber/v3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.52.13"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/gofiber/fiber/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.52.14"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45045"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-02T13:50:45Z",
    "nvd_published_at": "2026-07-08T20:16:50Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nThe `BalancerForward` proxy helper in GoFiber uses `Header.Add()` instead of `Header.Set()` when injecting the `X-Real-IP` header. This appends the real client IP as a second header value rather than replacing any attacker-supplied value. Upstream servers that read the first `X-Real-IP` header (nginx, Express, most HTTP servers) use the attacker\u0027s spoofed IP for logging, rate limiting, and access control.\n\n## Vulnerable Code\n\n**File:** `middleware/proxy/proxy.go`, lines 270-285\n\n```go\nfunc BalancerForward(servers []string, clients ...*fasthttp.Client) fiber.Handler {\n    r := \u0026roundrobin{\n        current: 0,\n        pool:    servers,\n    }\n    return func(c fiber.Ctx) error {\n        server := r.get()\n        if !strings.HasPrefix(server, \"http\") {\n            server = \"http://\" + server\n        }\n        c.Request().Header.Add(\"X-Real-IP\", c.IP())   // line 282: Add, not Set\n        return Do(c, server+c.OriginalURL(), clients...)\n    }\n}\n```\n\n## Data Flow\n\n1. Attacker sends request with `X-Real-IP: 10.0.0.1` (spoofed internal IP)\n2. `BalancerForward` handler executes at line 282\n3. `c.Request().Header.Add(\"X-Real-IP\", c.IP())` APPENDS the real IP as a second header\n4. Upstream server receives: `X-Real-IP: 10.0.0.1` AND `X-Real-IP: \u003creal-attacker-ip\u003e`\n5. Most HTTP servers (nginx, Node.js, Apache) read the FIRST value\n6. Upstream uses `10.0.0.1` for all IP-dependent logic\n\n## Impact\n\n- **Rate limit bypass:** IP-based rate limiting at the upstream uses the spoofed IP, allowing unlimited requests\n- **IP ACL bypass:** Internal IP allowlists (e.g., admin panels restricted to `10.0.0.0/8`) can be bypassed\n- **Audit log poisoning:** Security logs record the spoofed IP, making incident investigation unreliable\n- **Geolocation bypass:** IP-based geofencing or region restrictions are circumvented\n\n## Fix\n\nReplace `Header.Add()` with `Header.Set()` at line 282:\n\n```go\nc.Request().Header.Set(\"X-Real-IP\", c.IP())\n```\n\n`Header.Set()` replaces any existing header value, ensuring only the real client IP is forwarded.",
  "id": "GHSA-gcfq-8gqf-4876",
  "modified": "2026-08-04T21:52:02Z",
  "published": "2026-07-02T13:50:45Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/security/advisories/GHSA-gcfq-8gqf-4876"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45045"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/pull/4260"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/pull/4495"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/commit/1403cc8292da3220e9316960b4030cc722a0f396"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/commit/33c9501288ab47a429c8b5e701493f0c3c0af37d"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/gofiber/fiber"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/releases/tag/v2.52.14"
    },
    {
      "type": "WEB",
      "url": "https://github.com/gofiber/fiber/releases/tag/v3.3.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "GoFiber Vulnerable to X-Real-IP Spoofing via Header.Add() in BalancerForward"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-45045 (GCVE-0-2026-45045)

FKIE_CVE-2026-45045

GHSA-GCFQ-8GQF-4876

Summary

Vulnerable Code

Data Flow

Impact

Fix

Tags

Sightings

Nomenclature

Related by attack behaviour