Vulnerability-Lookup

UBUNTU-CVE-2025-66506 (CVE-2025-66506)

Vulnerability from osv_ubuntu – Published: 2025-12-04 22:15 – Updated: 2026-05-20 15:22 – Source website

Details

Fulcio is a free-to-use certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Prior to 1.8.3, function identity.extractIssuerURL splits (via a call to strings.Split) its argument (which is untrusted data) on periods. As a result, in the face of a malicious request with an (invalid) OIDC identity token in the payload containing many period characters, a call to extractIssuerURL incurs allocations to the tune of O(n) bytes (where n stands for the length of the function's argument), with a constant factor of about 16. This vulnerability is fixed in 1.8.3.

Severity

7.5 (High)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2025-66506	REPORT
	https://www.cve.org/CVERecord?id=CVE-2025-66506	REPORT
	https://github.com/sigstore/fulcio/commit/765a0e5…	REPORT
	https://github.com/sigstore/fulcio/security/advis…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "golang-github-sigstore-fulcio-dev",
            "binary_version": "1.6.5-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "golang-github-sigstore-fulcio",
        "purl": "pkg:deb/ubuntu/golang-github-sigstore-fulcio@1.6.5-1?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.5-1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "golang-github-sigstore-fulcio-dev",
            "binary_version": "1.7.1-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "golang-github-sigstore-fulcio",
        "purl": "pkg:deb/ubuntu/golang-github-sigstore-fulcio@1.7.1-1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.6.5-1",
        "1.7.1-1"
      ]
    }
  ],
  "aliases": [],
  "details": "Fulcio is a free-to-use certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Prior to 1.8.3, function identity.extractIssuerURL splits (via a call to strings.Split) its argument (which is untrusted data) on periods. As a result, in the face of a malicious request with an (invalid) OIDC identity token in the payload containing many period characters, a call to extractIssuerURL incurs allocations to the tune of O(n) bytes (where n stands for the length of the function\u0027s argument), with a constant factor of about 16. This vulnerability is fixed in 1.8.3.",
  "id": "UBUNTU-CVE-2025-66506",
  "modified": "2026-05-20T15:22:59Z",
  "published": "2025-12-04T22:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2025-66506"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-66506"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2025-66506"
  ]
}

CVE-2025-66506 (GCVE-0-2025-66506)

Vulnerability from cvelistv5 – Published: 2025-12-04 22:04 – Updated: 2025-12-05 15:32

Title

Fulcio allocates excessive memory during token parsing

Summary

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2025-12-05 15:32 UTC

CWE

CWE-405 - Asymmetric Resource Consumption (Amplification)

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7580 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/sigstore/fulcio/security/advis…	x_refsource_CONFIRM
https://github.com/sigstore/fulcio/commit/765a0e5…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
sigstore	fulcio	Affected: < 1.8.3

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-66506",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-12-05T15:32:15.086814Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2025-12-05T15:32:25.591Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "fulcio",
          "vendor": "sigstore",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.8.3"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Fulcio is a free-to-use certificate authority for issuing code signing certificates for an OpenID Connect (OIDC) identity. Prior to 1.8.3, function identity.extractIssuerURL splits (via a call to strings.Split) its argument (which is untrusted data) on periods. As a result, in the face of a malicious request with an (invalid) OIDC identity token in the payload containing many period characters, a call to extractIssuerURL incurs allocations to the tune of O(n) bytes (where n stands for the length of the function\u0027s argument), with a constant factor of about 16. This vulnerability is fixed in 1.8.3."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-405",
              "description": "CWE-405: Asymmetric Resource Consumption (Amplification)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-04T22:04:41.637Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw"
        },
        {
          "name": "https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a"
        }
      ],
      "source": {
        "advisory": "GHSA-f83f-xpx7-ffpw",
        "discovery": "UNKNOWN"
      },
      "title": "Fulcio allocates excessive memory during token parsing"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2025-66506",
    "datePublished": "2025-12-04T22:04:41.637Z",
    "dateReserved": "2025-12-03T15:12:22.978Z",
    "dateUpdated": "2025-12-05T15:32:25.591Z",
    "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.

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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UBUNTU-CVE-2025-66506 (CVE-2025-66506)

CVE-2025-66506 (GCVE-0-2025-66506)

Tags

Sightings

Nomenclature

Related by attack behaviour