Vulnerability-Lookup

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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JSON

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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"
}

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 (v2.0.3)

CWE

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

Assigner

EEF

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
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

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JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-47076",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
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                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-26T15:46:49.956392Z",
                "version": "2.0.3"
              },
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          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
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          }
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        "title": "CISA ADP Vulnrichment"
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    ],
    "cna": {
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          ],
          "packageName": "hackney",
          "packageURL": "pkg:hex/hackney",
          "product": "hackney",
          "programFiles": [
            "src/hackney_url.erl"
          ],
          "programRoutines": [
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            }
          ],
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          "vendor": "benoitc",
          "versions": [
            {
              "lessThan": "4.0.1",
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              "version": "0.13.0",
              "versionType": "semver"
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        },
        {
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          "cpes": [
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          "defaultStatus": "unaffected",
          "modules": [
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          "versions": [
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              "versionType": "git"
            }
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        }
      ],
      "cpeApplicability": [
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          "nodes": [
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              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:benoitc:hackney:*:*:*:*:*:*:*:*",
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        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Benoit Chesneau"
        },
        {
          "lang": "en",
          "type": "analyst",
          "value": "Jonatan M\u00e4nnchen / EEF"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "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."
        }
      ],
      "impacts": [
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          "capecId": "CAPEC-664",
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              "lang": "en",
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      "metrics": [
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          "cvssV4_0": {
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          "url": "https://github.com/benoitc/hackney/security/advisories/GHSA-pj7v-xfvx-wmjq"
        },
        {
          "tags": [
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          "url": "https://cna.erlef.org/cves/CVE-2026-47076.html"
        },
        {
          "tags": [
            "related"
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          "url": "https://osv.dev/vulnerability/EEF-CVE-2026-47076"
        },
        {
          "tags": [
            "patch"
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          "url": "https://github.com/benoitc/hackney/commit/452620a92ec1da2e6b4862a049a2a4f04b42068f"
        }
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      "source": {
        "discovery": "EXTERNAL"
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      "title": "SSRF allowlist bypass via percent-encoded host in hackney",
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    "assignerShortName": "EEF",
    "cveId": "CVE-2026-47076",
    "datePublished": "2026-05-25T14:00:46.707Z",
    "dateReserved": "2026-05-18T17:28:10.319Z",
    "dateUpdated": "2026-05-27T15:41:17.845Z",
    "state": "PUBLISHED"
  },
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}

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.

Action not permitted

GHSA-PJ7V-XFVX-WMJQ

Summary

Details

PoC

Impact

Resources

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

Tags

Sightings

Nomenclature