Vulnerability-Lookup

GHSA-FQ95-V8XC-JM3V

Vulnerability from github – Published: 2026-09-22 20:34 – Updated: 2026-09-22 20:34

Summary

Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header

Details

Affected: github.com/fabiolb/fabio >= 1.6.6 through 1.7.1 and master HEAD (c75f8a6).

Summary

The v1.6.6 fix for CVE-2025-48865 sweeps the client Connection header against a hardcoded allowlist protectHeaders (proxy/http_headers.go:28-36) containing only the 7 X-Forwarded family headers. Fabio also injects three operator-configured server-side trust headers that are NOT in that allowlist, so the original hop-by-hop stripping attack still works against them.

Details

The three unprotected trust headers and where fabio sets them: - ClientIPHeader (proxy.header.clientip) - http_headers.go:73 r.Header.Set(cfg.ClientIPHeader, remoteIP) - TLSHeader (proxy.header.tls) - http_headers.go:153 r.Header.Set(cfg.TLSHeader, cfg.TLSHeaderValue) (TLS connections) - RequestID (proxy.header.requestid) - http_proxy.go:90 r.Header.Set(p.Config.RequestID, id())

Order of operations in HTTPProxy.ServeHTTP: (1) line 90 sets RequestID; (2) line 175 calls addHeaders, which sweeps the Connection header (keeping the three configured names because they are absent from protectHeaders) and then sets ClientIPHeader/TLSHeader; (3) line 223 runs the Go httputil.ReverseProxy, whose removeHopByHopHeaders (Go stdlib net/http/httputil/reverseproxy.go) iterates the inbound Connection header and h.Dels every listed header. The three trust headers fabio just set are therefore deleted before the request reaches the backend.

PoC

Configure proxy.header.clientip=X-Client-IP, proxy.header.requestid=X-Request-ID. Raw request:

GET / HTTP/1.1
Host: foo.com
Connection: close, X-Client-IP, X-Request-ID

Backend sees X-Client-IP: <empty> and X-Request-ID: <empty>. Baseline (Connection: close) => backend sees the real client IP and a request id. The same works for proxy.header.tls over TLS (Connection: close, X-Secure strips the TLS assertion). Reproduced by the two PASS-ing tests in proxy/poc_cve48865_incomplete_test.go on master HEAD (Go 1.26.4). Control: X-Forwarded-For (in protectHeaders) survives, confirming the gap is specific to the configured headers.

Impact

Where a backend trusts these fabio-set headers, an external unauthenticated client can strip/downgrade the trust signal: bypass/poison IP-based ACL or audit that reads the clientip header, downgrade a TLS-terminated request to appear non-TLS to a backend keying off the TLS header, or drop request-id correlation. Scope: deployments that enable the relevant proxy.header.* option (all empty by default). Fix: add the configured ClientIPHeader/TLSHeader/RequestID names to the protectHeaders set (or strip their token from the inbound Connection header) inside addHeaders.

Parent: CVE-2025-48865 / GHSA-q7p4-7xjv-j3wf (fixed in v1.6.6). This is an incomplete-fix sibling - the same hop-by-hop stripping primitive applies to the operator-configured trust headers the allowlist does not cover.

Severity

5.8 (Medium)


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

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.7.1"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/fabiolb/fabio"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.6.6"
            },
            {
              "fixed": "1.7.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-62987"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-290",
      "CWE-348"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-22T20:34:22Z",
    "nvd_published_at": "2026-09-21T17:17:38Z",
    "severity": "MODERATE"
  },
  "details": "**Affected:** github.com/fabiolb/fabio \u003e= 1.6.6 through 1.7.1 and master HEAD (c75f8a6).\n\n### Summary\nThe v1.6.6 fix for CVE-2025-48865 sweeps the client `Connection` header against a hardcoded allowlist `protectHeaders` (proxy/http_headers.go:28-36) containing only the 7 X-Forwarded family headers. Fabio also injects three *operator-configured* server-side trust headers that are NOT in that allowlist, so the original hop-by-hop stripping attack still works against them.\n\n### Details\nThe three unprotected trust headers and where fabio sets them:\n- ClientIPHeader (`proxy.header.clientip`) - http_headers.go:73 `r.Header.Set(cfg.ClientIPHeader, remoteIP)`\n- TLSHeader (`proxy.header.tls`) - http_headers.go:153 `r.Header.Set(cfg.TLSHeader, cfg.TLSHeaderValue)` (TLS connections)\n- RequestID (`proxy.header.requestid`) - http_proxy.go:90 `r.Header.Set(p.Config.RequestID, id())`\n\nOrder of operations in HTTPProxy.ServeHTTP: (1) line 90 sets RequestID; (2) line 175 calls addHeaders, which sweeps the Connection header (keeping the three configured names because they are absent from protectHeaders) and then sets ClientIPHeader/TLSHeader; (3) line 223 runs the Go `httputil.ReverseProxy`, whose `removeHopByHopHeaders` (Go stdlib net/http/httputil/reverseproxy.go) iterates the inbound `Connection` header and `h.Del`s every listed header. The three trust headers fabio just set are therefore deleted before the request reaches the backend.\n\n### PoC\nConfigure `proxy.header.clientip=X-Client-IP`, `proxy.header.requestid=X-Request-ID`. Raw request:\n```\nGET / HTTP/1.1\nHost: foo.com\nConnection: close, X-Client-IP, X-Request-ID\n```\nBackend sees `X-Client-IP: \u003cempty\u003e` and `X-Request-ID: \u003cempty\u003e`. Baseline (`Connection: close`) =\u003e backend sees the real client IP and a request id. The same works for `proxy.header.tls` over TLS (`Connection: close, X-Secure` strips the TLS assertion). Reproduced by the two PASS-ing tests in proxy/poc_cve48865_incomplete_test.go on master HEAD (Go 1.26.4). Control: `X-Forwarded-For` (in protectHeaders) survives, confirming the gap is specific to the configured headers.\n\n### Impact\nWhere a backend trusts these fabio-set headers, an external unauthenticated client can strip/downgrade the trust signal: bypass/poison IP-based ACL or audit that reads the clientip header, downgrade a TLS-terminated request to appear non-TLS to a backend keying off the TLS header, or drop request-id correlation. Scope: deployments that enable the relevant `proxy.header.*` option (all empty by default). Fix: add the configured ClientIPHeader/TLSHeader/RequestID names to the protectHeaders set (or strip their token from the inbound Connection header) inside addHeaders.\n\nParent: CVE-2025-48865 / GHSA-q7p4-7xjv-j3wf (fixed in v1.6.6). This is an incomplete-fix sibling - the same hop-by-hop stripping primitive applies to the operator-configured trust headers the allowlist does not cover.",
  "id": "GHSA-fq95-v8xc-jm3v",
  "modified": "2026-09-22T20:34:22Z",
  "published": "2026-09-22T20:34:22Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/fabiolb/fabio/security/advisories/GHSA-fq95-v8xc-jm3v"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-62987"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fabiolb/fabio/commit/240526a8004077edad4fb96d25b382bfc3901357"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/fabiolb/fabio"
    },
    {
      "type": "WEB",
      "url": "https://github.com/fabiolb/fabio/releases/tag/v1.7.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header"
}

CVE-2026-62987 (GCVE-0-2026-62987)

Vulnerability from cvelistv5 – Published: 2026-09-21 16:11 – Updated: 2026-09-21 18:04

Title

Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header

Summary

Fabio is an HTTP(S) and TCP router for deploying applications managed by consul. From 1.6.6 until 1.7.2, the CVE-2025-48865 fix in proxy/http_headers.go uses protectHeaders for a hardcoded set of forwarded headers but omits the operator-configured ClientIPHeader, TLSHeader, and RequestID names. In proxy/http_proxy.go, HTTPProxy.ServeHTTP calls addHeaders to set these trust headers before Go ReverseProxy processes the inbound Connection header, allowing an unauthenticated client to name and remove the configured headers before the request reaches the backend. Deployments that enable the corresponding proxy.header options can therefore lose client-IP, TLS-termination, or request-correlation signals used by backend authorization and auditing; the options are empty by default, and the hardcoded protected forwarded headers are unaffected. This issue is fixed in version 1.7.2.

Severity

5.8 (Medium)


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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-21 18:03 UTC

CWE

CWE-290 - Authentication Bypass by Spoofing
CWE-348 - Use of Less Trusted Source

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7619 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/fabiolb/fabio/security/advisor…	x_refsource_CONFIRM
https://github.com/fabiolb/fabio/commit/240526a80…	x_refsource_MISC
https://github.com/fabiolb/fabio/releases/tag/v1.7.2	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
fabiolb	fabio	Affected: >= 1.6.6, < 1.7.2

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-62987",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-21T18:03:21.616808Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-21T18:04:03.288Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/fabiolb/fabio/security/advisories/GHSA-fq95-v8xc-jm3v"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "fabio",
          "vendor": "fabiolb",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 1.6.6, \u003c 1.7.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Fabio is an HTTP(S) and TCP router for deploying applications managed by consul. From 1.6.6 until 1.7.2, the CVE-2025-48865 fix in proxy/http_headers.go uses protectHeaders for a hardcoded set of forwarded headers but omits the operator-configured ClientIPHeader, TLSHeader, and RequestID names. In proxy/http_proxy.go, HTTPProxy.ServeHTTP calls addHeaders to set these trust headers before Go ReverseProxy processes the inbound Connection header, allowing an unauthenticated client to name and remove the configured headers before the request reaches the backend. Deployments that enable the corresponding proxy.header options can therefore lose client-IP, TLS-termination, or request-correlation signals used by backend authorization and auditing; the options are empty by default, and the hardcoded protected forwarded headers are unaffected. This issue is fixed in version 1.7.2."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-348",
              "description": "CWE-348: Use of Less Trusted Source",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-21T16:11:21.044Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/fabiolb/fabio/security/advisories/GHSA-fq95-v8xc-jm3v",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/fabiolb/fabio/security/advisories/GHSA-fq95-v8xc-jm3v"
        },
        {
          "name": "https://github.com/fabiolb/fabio/commit/240526a8004077edad4fb96d25b382bfc3901357",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/fabiolb/fabio/commit/240526a8004077edad4fb96d25b382bfc3901357"
        },
        {
          "name": "https://github.com/fabiolb/fabio/releases/tag/v1.7.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/fabiolb/fabio/releases/tag/v1.7.2"
        }
      ],
      "source": {
        "advisory": "GHSA-fq95-v8xc-jm3v",
        "discovery": "UNKNOWN"
      },
      "title": "Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-62987",
    "datePublished": "2026-09-21T16:11:21.044Z",
    "dateReserved": "2026-07-14T22:48:09.781Z",
    "dateUpdated": "2026-09-21T18:04:03.288Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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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.

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.
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Action not permitted

GHSA-FQ95-V8XC-JM3V

Summary

Details

PoC

Impact

CVE-2026-62987 (GCVE-0-2026-62987)

Tags

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