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FKIE_CVE-2026-75870

Vulnerability from fkie_nvd - Published: 2026-08-22 14:16 - Updated: 2026-08-26 16:51
Severity
9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Summary
Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret. The session keyword freezes its options onto the application as given: it does not require a secret, warn, or refuse to start when one is absent. The cookie read and the write-back both default that key to the empty string, so a declaration with no secret option, or with an undefined or empty one, signs and verifies with a zero-length HMAC-SHA256 key. An attacker who knows the cookie format can then mint one offline carrying any contents the session holds, such as a user identifier or a role. Nothing marks the misconfiguration at runtime: cookies are well formed and sessions round-trip as expected.
References
9b29abf9-4ab0-4765-b253-1875cd9b441ehttps://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h
9b29abf9-4ab0-4765-b253-1875cd9b441ehttps://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm
9b29abf9-4ab0-4765-b253-1875cd9b441ehttps://metacpan.org/release/LNATION/Punk-0.18/source/Changes
af854a3a-2127-422b-91ae-364da2661108http://www.openwall.com/lists/oss-security/2026/08/22/5
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "modules": [
            "Punk"
          ],
          "packageName": "Punk",
          "packageURL": "pkg:cpan/Punk",
          "programFiles": [
            "xs/app.xs",
            "include/punk/punk_session.h"
          ],
          "programRoutines": [
            {
              "name": "Punk::App::session"
            },
            {
              "name": "ps_load"
            },
            {
              "name": "ps_writeback"
            }
          ],
          "versions": [
            {
              "lessThan": "0.18",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Punk versions before 0.18 for Perl allow session cookie forgery via an empty default HMAC key when a session is declared without a secret.\n\nThe session keyword freezes its options onto the application as given: it does not require a secret, warn, or refuse to start when one is absent. The cookie read and the write-back both default that key to the empty string, so a declaration with no secret option, or with an undefined or empty one, signs and verifies with a zero-length HMAC-SHA256 key.\n\nAn attacker who knows the cookie format can then mint one offline carrying any contents the session holds, such as a user identifier or a role. Nothing marks the misconfiguration at runtime: cookies are well formed and sessions round-trip as expected."
    }
  ],
  "id": "CVE-2026-75870",
  "lastModified": "2026-08-26T16:51:19.490",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 9.1,
          "baseSeverity": "CRITICAL",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.2,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-75870",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-25T19:27:34.454527Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-22T14:16:33.813",
  "references": [
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/release/LNATION/Punk-0.18/source/Changes"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/08/22/5"
    }
  ],
  "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-1394"
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "type": "Secondary"
    }
  ]
}



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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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