Vulnerability-Lookup

GHSA-3679-XR9W-9625

Vulnerability from github – Published: 2026-08-22 15:31 – Updated: 2026-08-22 21:31

Details

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.

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JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-75870"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1394"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-22T14:16:33Z",
    "severity": null
  },
  "details": "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": "GHSA-3679-xr9w-9625",
  "modified": "2026-08-22T21:31:02Z",
  "published": "2026-08-22T15:31:03Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-75870"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/LNATION/Punk-0.18/source/Changes"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/08/22/5"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-75870 (GCVE-0-2026-75870)

Vulnerability from cvelistv5 – Published: 2026-08-22 13:35 – Updated: 2026-08-22 19:07

Title

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

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.

Severity

No CVSS data available.

CWE

CWE-1394 - Use of Default Cryptographic Key

Assigner

CPANSec redhat root

References

4 references

URL	Tags
https://metacpan.org/release/LNATION/Punk-0.17/so…	technical-description
https://metacpan.org/release/LNATION/Punk-0.17/vi…	technical-description
https://metacpan.org/release/LNATION/Punk-0.18/so…	release-notes
http://www.openwall.com/lists/oss-security/2026/08/22/5

Impacted products

1 product

Vendor	Product	Version
		Affected: 0 , < 0.18 (custom)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-08-22T19:07:10.053Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/08/22/5"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "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"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1394",
              "description": "CWE-1394 Use of Default Cryptographic Key",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-22T13:35:58.346Z",
        "orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
        "shortName": "CPANSec"
      },
      "references": [
        {
          "tags": [
            "technical-description"
          ],
          "url": "https://metacpan.org/release/LNATION/Punk-0.17/source/include/punk/punk_session.h"
        },
        {
          "tags": [
            "technical-description"
          ],
          "url": "https://metacpan.org/release/LNATION/Punk-0.17/view/lib/Punk.pm"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://metacpan.org/release/LNATION/Punk-0.18/source/Changes"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to Punk 0.18 or later."
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "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",
      "workarounds": [
        {
          "lang": "en",
          "value": "For deployments that cannot upgrade to 0.18, declare the session keyword with a non-empty secret. The secret keyword fails closed, so sourcing the key through it turns a missing configuration path or an unset environment variable into a startup error."
        }
      ],
      "x_generator": {
        "engine": "cpansec-cna-tool 0.1"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
    "assignerShortName": "CPANSec",
    "cveId": "CVE-2026-75870",
    "datePublished": "2026-08-22T13:35:58.346Z",
    "dateReserved": "2026-08-18T11:59:49.642Z",
    "dateUpdated": "2026-08-22T19:07:10.053Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Action not permitted

GHSA-3679-XR9W-9625

CVE-2026-75870 (GCVE-0-2026-75870)

Tags

Sightings

Nomenclature