Vulnerability-Lookup

GHSA-CCC2-34G9-J7RG

Vulnerability from github – Published: 2026-07-20 09:31 – Updated: 2026-07-20 15:32

Details

Dancer2 versions through 2.1.0 for Perl generate insecure session ids when CSPRNG modules are unavailable.

Dancer2::Core::Role::SessionFactory::generate_id silently falls back to a built-in rand-derived session id when both Math::Random::ISAAC::XS and Crypt::URandom are unavailable.

The fallback session id is generated from a SHA-1 hash of a call to the built-in rand function, the absolute path of the Dancer2::Core::Role::SessionFactory module, an internal counter, the process id, the module instance memory address, and a shuffled string of characters (using the List::Util::shuffle function, which also uses the built-in rand function).

These are all low-entropy and easily guessed sources.

The built-in rand() function is seeded with 32-bits and considered unsuitable for security applications.

Predictable session ids could allow an attacker to gain access to systems.

Severity

8.2 (High)


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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-13577"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-338"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-20T08:16:28Z",
    "severity": "HIGH"
  },
  "details": "Dancer2 versions through 2.1.0 for Perl generate insecure session ids when CSPRNG modules are unavailable.\n\nDancer2::Core::Role::SessionFactory::generate_id silently falls back to a built-in rand-derived session id when both Math::Random::ISAAC::XS and Crypt::URandom are unavailable.\n\nThe fallback session id is generated from a SHA-1 hash of a call to the built-in rand function, the absolute path of the Dancer2::Core::Role::SessionFactory module, an internal counter, the process id, the module instance memory address, and a shuffled string of characters (using the List::Util::shuffle function, which also uses the built-in rand function).\n\nThese are all low-entropy and easily guessed sources.\n\nThe built-in rand() function is seeded with 32-bits and considered unsuitable for security applications.\n\nPredictable session ids could allow an attacker to gain access to systems.",
  "id": "GHSA-ccc2-34g9-j7rg",
  "modified": "2026-07-20T15:32:03Z",
  "published": "2026-07-20T09:31:08Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-13577"
    },
    {
      "type": "WEB",
      "url": "https://github.com/PerlDancer/Dancer2/blob/v2.1.0/lib/Dancer2/Core/Role/SessionFactory.pm#L142"
    },
    {
      "type": "WEB",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-5080"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-13577 (GCVE-0-2026-13577)

Vulnerability from cvelistv5 – Published: 2026-07-20 07:11 – Updated: 2026-07-22 12:00

Title

Dancer2 versions through 2.1.0 for Perl generate insecure session ids when required CSPRNG modules are unavailable

Summary

Dancer2 versions through 2.1.0 for Perl generate insecure session ids when required CSPRNG modules are unavailable. Dancer2::Core::Role::SessionFactory::generate_id silently falls back to a built-in rand-derived session id unless both Math::Random::ISAAC::XS and Crypt::URandom are available. The fallback session id is generated from a SHA-1 hash of a call to the built-in rand function, the absolute path of the Dancer2::Core::Role::SessionFactory module, an internal counter, the process id, the module instance memory address, and a shuffled string of characters (using the List::Util::shuffle function, which also uses the built-in rand function). These are all low-entropy and easily guessed sources. The built-in rand() function is seeded with 32-bits and considered unsuitable for security applications. Predictable session ids could allow an attacker to gain access to systems.

Severity

8.2 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-340 - Generation of Predictable Numbers or Identifiers
CWE-338 - Use of Cryptographically Weak Pseudo-Random Number Generator

Assigner

CPANSec

References

2 references

URL	Tags
https://github.com/PerlDancer/Dancer2/blob/v2.1.0…
https://www.cve.org/CVERecord?id=CVE-2026-5080	related

Impacted products

1 product

Vendor	Product	Version
CROMEDOME	Dancer2	Affected: 0 , ≤ 2.1.0 (custom)

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 8.2,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "LOW",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-13577",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-20T13:05:03.182340Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-20T13:05:10.916Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "packageName": "Dancer2",
          "product": "Dancer2",
          "programFiles": [
            "lib/Dancer2/Core/Role/SessionFactory.pm"
          ],
          "programRoutines": [
            {
              "name": "Dancer2::Core::Role::SessionFactory::generate_id"
            }
          ],
          "repo": "https://github.com/PerlDancer/Dancer2",
          "vendor": "CROMEDOME",
          "versions": [
            {
              "lessThanOrEqual": "2.1.0",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Dancer2 versions through 2.1.0 for Perl generate insecure session ids when required CSPRNG modules are unavailable.\n\nDancer2::Core::Role::SessionFactory::generate_id silently falls back to a built-in rand-derived session id unless both Math::Random::ISAAC::XS and Crypt::URandom are available.\n\nThe fallback session id is generated from a SHA-1 hash of a call to the built-in rand function, the absolute path of the Dancer2::Core::Role::SessionFactory module, an internal counter, the process id, the module instance memory address, and a shuffled string of characters (using the List::Util::shuffle function, which also uses the built-in rand function).\n\nThese are all low-entropy and easily guessed sources.\n\nThe built-in rand() function is seeded with 32-bits and considered unsuitable for security applications.\n\nPredictable session ids could allow an attacker to gain access to systems."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-115",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-115 Authentication Bypass"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-340",
              "description": "CWE-340 Generation of Predictable Numbers or Identifiers",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-338",
              "description": "CWE-338 Use of Cryptographically Weak Pseudo-Random Number Generator",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-22T12:00:11.288Z",
        "orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
        "shortName": "CPANSec"
      },
      "references": [
        {
          "url": "https://github.com/PerlDancer/Dancer2/blob/v2.1.0/lib/Dancer2/Core/Role/SessionFactory.pm#L142"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://www.cve.org/CVERecord?id=CVE-2026-5080"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Dancer2 versions through 2.1.0 for Perl generate insecure session ids when required CSPRNG modules are unavailable",
      "workarounds": [
        {
          "lang": "en",
          "value": "Ensure Crypt::URandom and Math::Random::ISAAC::XS modules are installed in the application PERL5LIB path."
        }
      ],
      "x_generator": {
        "engine": "cpansec-cna-tool 0.1"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
    "assignerShortName": "CPANSec",
    "cveId": "CVE-2026-13577",
    "datePublished": "2026-07-20T07:11:10.403Z",
    "dateReserved": "2026-06-28T20:59:07.978Z",
    "dateUpdated": "2026-07-22T12:00:11.288Z",
    "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.

Action not permitted

GHSA-CCC2-34G9-J7RG

CVE-2026-13577 (GCVE-0-2026-13577)

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Sightings

Nomenclature