Vulnerability-Lookup

CVE-2026-47076 (GCVE-0-2026-47076)

Vulnerability from cvelistv5 – Published: 2026-05-25 14:00 – Updated: 2026-05-27 15:41

Title

SSRF allowlist bypass via percent-encoded host in hackney

Summary

Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackney_url{} record. OTP's uri_string:parse/1 and inet:parse_address/1 do not decode percent-escapes in the host, so a URL such as http://%31%32%37%2E%30%2E%30%2E%31/ is seen by a caller's allowlist validator with host %31%32%37%2E%30%2E%30%2E%31 (not an IP address), which passes the allowlist check. hackney's normalizer then decodes the host to 127.0.0.1 and opens a TCP connection to loopback. Because hackney:request/5 always calls hackney_url:normalize/2 with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost. This issue affects hackney: from 0.13.0 before 4.0.1.

Severity

6.9 (Medium)


                        
                          CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-26 15:46 UTC

CWE

CWE-436 - Interpretation Conflict
CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

EEF mitre root

References

4 references

URL	Tags
https://github.com/benoitc/hackney/security/advis…	vendor-advisoryrelated
https://cna.erlef.org/cves/CVE-2026-47076.html	related
https://osv.dev/vulnerability/EEF-CVE-2026-47076	related
https://github.com/benoitc/hackney/commit/452620a…	patch

Impacted products

2 products

Vendor	Product	Version	CPE status
benoitc	hackney	Affected: 0.13.0 , < 4.0.1 (semver) cpe:2.3:a:benoitc:hackney::::::::
benoitc	hackney	Affected: 4d725507588942fd00efca15b86da3273656510a , < 452620a92ec1da2e6b4862a049a2a4f04b42068f (git) cpe:2.3:a:benoitc:hackney::::::::

Credits

Ganbagana Benoit Chesneau Jonatan Männchen / EEF

Show details on NVD website

JSON

To clipboard

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      "title": "SSRF allowlist bypass via percent-encoded host in hackney",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47076.json",
      "version": "3"
    },
    "vulnrichment": {
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            "metrics": [
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              "defaultStatus": "unaffected",
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              "packageName": "benoitc/hackney",
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              "product": "hackney",
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              "value": "Ganbagana"
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              "lang": "en",
              "type": "remediation developer",
              "value": "Benoit Chesneau"
            },
            {
              "lang": "en",
              "type": "analyst",
              "value": "Jonatan M\u00e4nnchen / EEF"
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          ],
          "descriptions": [
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                  "value": "Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery.\u003cp\u003e\u003ctt\u003ehackney_url:normalize/2\u003c/tt\u003e URL-decodes the host component after the URL has been parsed into a \u003ctt\u003e#hackney_url{}\u003c/tt\u003e record. OTP\u0027s \u003ctt\u003euri_string:parse/1\u003c/tt\u003e and \u003ctt\u003einet:parse_address/1\u003c/tt\u003e do not decode percent-escapes in the host, so a URL such as \u003ctt\u003ehttp://%31%32%37%2E%30%2E%30%2E%31/\u003c/tt\u003e is seen by a caller\u0027s allowlist validator with host \u003ctt\u003e%31%32%37%2E%30%2E%30%2E%31\u003c/tt\u003e (not an IP address), which passes the allowlist check. hackney\u0027s normalizer then decodes the host to \u003ctt\u003e127.0.0.1\u003c/tt\u003e and opens a TCP connection to loopback. Because \u003ctt\u003ehackney:request/5\u003c/tt\u003e always calls \u003ctt\u003ehackney_url:normalize/2\u003c/tt\u003e with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost.\u003c/p\u003e\u003cp\u003eThis issue affects hackney: from 0.13.0 before 4.0.1.\u003c/p\u003e"
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              "value": "Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackney_url{} record. OTP\u0027s uri_string:parse/1 and inet:parse_address/1 do not decode percent-escapes in the host, so a URL such as http://%31%32%37%2E%30%2E%30%2E%31/ is seen by a caller\u0027s allowlist validator with host %31%32%37%2E%30%2E%30%2E%31 (not an IP address), which passes the allowlist check. hackney\u0027s normalizer then decodes the host to 127.0.0.1 and opens a TCP connection to loopback. Because hackney:request/5 always calls hackney_url:normalize/2 with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost.\n\nThis issue affects hackney: from 0.13.0 before 4.0.1."
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        "datePublished": "2026-05-25T14:00:46.707Z",
        "dateReserved": "2026-05-18T17:28:10.319Z",
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}

FKIE_CVE-2026-47076

Vulnerability from fkie_nvd - Published: 2026-05-25 15:16 - Updated: 2026-07-24 10:10

Severity

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

Summary

References

URL	Tags
6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://cna.erlef.org/cves/CVE-2026-47076.html	Patch, Third Party Advisory
6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f	Patch
6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq	Exploit, Patch, Vendor Advisory
6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://osv.dev/vulnerability/EEF-CVE-2026-47076	Patch, Third Party Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq	Exploit, Patch, Vendor Advisory

Impacted products

	Vendor	Product	Version
	benoitc	hackney	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "hackney_url"
          ],
          "packageName": "hackney",
          "packageURL": "pkg:hex/hackney",
          "product": "hackney",
          "programFiles": [
            "src/hackney_url.erl"
          ],
          "programRoutines": [
            {
              "name": "hackney_url:normalize/2"
            }
          ],
          "repo": "https://github.com/benoitc/hackney",
          "vendor": "benoitc",
          "versions": [
            {
              "lessThan": "4.0.1",
              "status": "affected",
              "version": "0.13.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "hackney_url"
          ],
          "packageName": "benoitc/hackney",
          "packageURL": "pkg:github/benoitc/hackney",
          "product": "hackney",
          "programFiles": [
            "src/hackney_url.erl"
          ],
          "programRoutines": [
            {
              "name": "hackney_url:normalize/2"
            }
          ],
          "repo": "https://github.com/benoitc/hackney",
          "vendor": "benoitc",
          "versions": [
            {
              "lessThan": "452620a92ec1da2e6b4862a049a2a4f04b42068f",
              "status": "affected",
              "version": "4d725507588942fd00efca15b86da3273656510a",
              "versionType": "git"
            }
          ]
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "345EDE12-0BFF-4AE1-90F9-F54561A7B64F",
              "versionEndExcluding": "4.0.1",
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              "vulnerable": true
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          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Interpretation Conflict vulnerability in benoitc hackney allows Server Side Request Forgery. hackney_url:normalize/2 URL-decodes the host component after the URL has been parsed into a #hackney_url{} record. OTP\u0027s uri_string:parse/1 and inet:parse_address/1 do not decode percent-escapes in the host, so a URL such as http://%31%32%37%2E%30%2E%30%2E%31/ is seen by a caller\u0027s allowlist validator with host %31%32%37%2E%30%2E%30%2E%31 (not an IP address), which passes the allowlist check. hackney\u0027s normalizer then decodes the host to 127.0.0.1 and opens a TCP connection to loopback. Because hackney:request/5 always calls hackney_url:normalize/2 with no opt-out, every request that takes a binary or list URL is affected. The same technique reaches cloud instance metadata services (169.254.169.254), RFC1918 networks, and any admin interface listening on localhost.\n\nThis issue affects hackney: from 0.13.0 before 4.0.1."
    },
    {
      "lang": "es",
      "value": "Vulnerabilidad de conflicto de interpretaci\u00f3n en benoitc hackney permite la falsificaci\u00f3n de solicitudes del lado del servidor. hackney_url:normalize/2 decodifica URL el componente de host despu\u00e9s de que la URL ha sido analizada en un registro #hackney_url{}. uri_string:parse/1 e inet:parse_address/1 de OTP no decodifican los escapes de porcentaje en el host, por lo que una URL como http://%31%32%37%2E%30%2E%30%2E%31/ es vista por el validador de lista de permitidos de un llamador con el host %31%32%37%2E%30%2E%30%2E%31 (no una direcci\u00f3n IP), lo que pasa la verificaci\u00f3n de la lista de permitidos. El normalizador de hackney luego decodifica el host a 127.0.0.1 y abre una conexi\u00f3n TCP a loopback. Debido a que hackney:request/5 siempre llama a hackney_url:normalize/2 sin opci\u00f3n de exclusi\u00f3n, cada solicitud que toma una URL binaria o de lista se ve afectada. La misma t\u00e9cnica alcanza los servicios de metadatos de instancias en la nube (169.254.169.254), redes RFC1918 y cualquier interfaz de administraci\u00f3n escuchando en localhost.\n\nEste problema afecta a hackney: desde 0.13.0 antes de 4.0.1."
    }
  ],
  "id": "CVE-2026-47076",
  "lastModified": "2026-07-24T10:10:00.197",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "NONE",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.0,
        "impactScore": 4.0,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
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          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.9,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "HIGH",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
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          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary"
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    "ssvcV203": [
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        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-47076",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-05-26T15:46:49.956392Z",
          "version": "2.0.3"
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  "published": "2026-05-25T15:16:22.690",
  "references": [
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      "tags": [
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      "url": "https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f"
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  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
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}

GHSA-PJ7V-XFVX-WMJQ

Vulnerability from github – Published: 2026-06-26 21:54 – Updated: 2026-06-26 21:54

Summary

Hackney has SSRF allowlist bypass in hackney_url:normalize/2 via percent-encoded host

Details

Summary

hackney_url:normalize/2 URL-decodes the host component of a parsed URL, but the caller's SSRF allowlist runs before normalization using OTP's uri_string:parse/1 and inet:parse_address/1, neither of which decodes percent-escapes in hostnames. A URL like http://%31%32%37%2E%30%2E%30%2E%31/ presents an encoded, non-IP-looking host to the validator, which passes the allowlist check; hackney's normalizer then decodes it to 127.0.0.1 and connects to loopback. Because hackney:request/5 always calls normalize/2 with no opt-out, every request path that accepts a binary or list URL is affected. This is a parser-differential SSRF in the same class as CVE-2025-1211, but in a different function.

Details

In src/hackney_url.erl (lines 161–186), normalize/2 checks whether the parsed host is already a dotted-quad or IPv6 literal via inet_parse:address/1. Percent-encoded forms like %31%32%37%2E%30%2E%30%2E%31 fail that check and fall into the catch-all branch, where urldecode/1 decodes the host before passing it to IDNA conversion:

Host1 = binary_to_list(
           urldecode(unicode:characters_to_binary(Host0))
         ),

The decoded host ("127.0.0.1") replaces the original in the returned #hackney_url{} record. hackney:request/5 at src/hackney.erl:463 always calls normalize/2, so the decoded host is what do_dispatch/1 and add_host_header/2 ultimately use. The on-wire Host: header and the TCP connect target both reflect the decoded value.

The same payload pattern reaches the AWS/GCP/Azure IMDS (169.254.169.254), RFC1918 ranges, and any localhost admin endpoint. The 1.21.0 patch for CVE-2025-1211 fixed a separate differential in parse_url/1 and did not touch normalize/2.

PoC

Validate the URL with the canonical Erlang SSRF allowlist: uri_string:parse/1 returns host <<"%31%32%37%2E%30%2E%30%2E%31">>, inet:parse_address/1 returns {error, einval}, so the allowlist accepts it.
Pass the same URL to hackney:get/1.
hackney's normalize/2 decodes the host to "127.0.0.1" and connects to 127.0.0.1:80. The internal service receives the request with Host: 127.0.0.1.

Impact

Unauthenticated SSRF bypassing the canonical Erlang allowlist pattern. Affects hackney 0.13.0 through 4.0.0 for any application that accepts attacker-supplied URLs. Targets include cloud IMDS endpoints, localhost admin interfaces, and RFC1918 backends. CVSS v4.0: 6.9 (MEDIUM).

Resources

Introduction commit: https://github.com/benoitc/hackney/commit/4d725507588942fd00efca15b86da3273656510a
Patch commit: https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f

Severity

6.9 (Medium)


                  
                    CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Hex",
        "name": "hackney"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.13.0"
            },
            {
              "fixed": "4.0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-47076"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-436",
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-26T21:54:55Z",
    "nvd_published_at": "2026-05-25T15:16:22Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\n`hackney_url:normalize/2` URL-decodes the host component of a parsed URL, but the caller\u0027s SSRF allowlist runs before normalization using OTP\u0027s `uri_string:parse/1` and `inet:parse_address/1`, neither of which decodes percent-escapes in hostnames. A URL like `http://%31%32%37%2E%30%2E%30%2E%31/` presents an encoded, non-IP-looking host to the validator, which passes the allowlist check; hackney\u0027s normalizer then decodes it to `127.0.0.1` and connects to loopback. Because `hackney:request/5` always calls `normalize/2` with no opt-out, every request path that accepts a binary or list URL is affected. This is a parser-differential SSRF in the same class as CVE-2025-1211, but in a different function.\n\n### Details\n\nIn `src/hackney_url.erl` (lines 161\u2013186), `normalize/2` checks whether the parsed host is already a dotted-quad or IPv6 literal via `inet_parse:address/1`. Percent-encoded forms like `%31%32%37%2E%30%2E%30%2E%31` fail that check and fall into the catch-all branch, where `urldecode/1` decodes the host before passing it to IDNA conversion:\n\n```erlang\nHost1 = binary_to_list(\n           urldecode(unicode:characters_to_binary(Host0))\n         ),\n```\n\nThe decoded host (`\"127.0.0.1\"`) replaces the original in the returned `#hackney_url{}` record. `hackney:request/5` at `src/hackney.erl:463` always calls `normalize/2`, so the decoded host is what `do_dispatch/1` and `add_host_header/2` ultimately use. The on-wire `Host:` header and the TCP connect target both reflect the decoded value.\n\nThe same payload pattern reaches the AWS/GCP/Azure IMDS (`169.254.169.254`), RFC1918 ranges, and any `localhost` admin endpoint. The 1.21.0 patch for CVE-2025-1211 fixed a separate differential in `parse_url/1` and did not touch `normalize/2`.\n\n### PoC\n\n1. Validate the URL with the canonical Erlang SSRF allowlist: `uri_string:parse/1` returns host `\u003c\u003c\"%31%32%37%2E%30%2E%30%2E%31\"\u003e\u003e`, `inet:parse_address/1` returns `{error, einval}`, so the allowlist accepts it.\n2. Pass the same URL to `hackney:get/1`.\n3. hackney\u0027s `normalize/2` decodes the host to `\"127.0.0.1\"` and connects to `127.0.0.1:80`. The internal service receives the request with `Host: 127.0.0.1`.\n\n### Impact\n\nUnauthenticated SSRF bypassing the canonical Erlang allowlist pattern. Affects hackney 0.13.0 through 4.0.0 for any application that accepts attacker-supplied URLs. Targets include cloud IMDS endpoints, `localhost` admin interfaces, and RFC1918 backends. CVSS v4.0: **6.9 (MEDIUM)**.\n\n## Resources\n\n* Introduction commit: https://github.com/benoitc/hackney/commit/4d725507588942fd00efca15b86da3273656510a\n* Patch commit: https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f",
  "id": "GHSA-pj7v-xfvx-wmjq",
  "modified": "2026-06-26T21:54:55Z",
  "published": "2026-06-26T21:54:55Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-47076"
    },
    {
      "type": "WEB",
      "url": "https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f"
    },
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-47076.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/benoitc/hackney"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-47076"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Hackney has SSRF allowlist bypass in hackney_url:normalize/2 via percent-encoded host"
}

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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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

CVE-2026-47076 (GCVE-0-2026-47076)

FKIE_CVE-2026-47076

GHSA-PJ7V-XFVX-WMJQ

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