Vulnerability-Lookup

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

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

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 mitre root

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	CPE status
sigstore	fulcio	Affected: < 1.8.3	guessed

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",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2025-66506",
      "date": "2026-09-17",
      "epss": "0.00211",
      "percentile": "0.11606"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-66506\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2025-12-04T22:15:49.503\",\"lastModified\":\"2026-06-17T09:56:57.130\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"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.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"sigstore\",\"product\":\"fulcio\",\"versions\":[{\"version\":\"\u003c 1.8.3\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2025-12-05T15:32:15.086814Z\",\"id\":\"CVE-2025-66506\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-405\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:linuxfoundation:fulcio:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"1.8.3\",\"matchCriteriaId\":\"C4901884-0820-47DE-B4A7-E79A053D360D\"}]}]}],\"references\":[{\"url\":\"https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw\",\"source\":\"security-advisories@github.com\",\"tags\":[\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-17T12:07:49+00:00",
      "cve": "CVE-2025-66506",
      "id": "CVE-2025-66506",
      "initial_release_date": "2025-12-04T22:04:41.637000+00:00",
      "product_status:fixed": "329",
      "product_status:known_affected": "42",
      "product_status:known_not_affected": "1297",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "github.com/sigstore/fulcio: Fulcio: Denial of Service via crafted OpenID Connect (OIDC) token",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-66506.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2025-66506\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2025-12-05T15:32:15.086814Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2025-12-05T15:32:21.138Z\"}}], \"cna\": {\"title\": \"Fulcio allocates excessive memory during token parsing\", \"source\": {\"advisory\": \"GHSA-f83f-xpx7-ffpw\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}}], \"affected\": [{\"vendor\": \"sigstore\", \"product\": \"fulcio\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 1.8.3\"}]}], \"references\": [{\"url\": \"https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw\", \"name\": \"https://github.com/sigstore/fulcio/security/advisories/GHSA-f83f-xpx7-ffpw\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a\", \"name\": \"https://github.com/sigstore/fulcio/commit/765a0e57608b9ef390e1eeeea8595b9054c63a5a\", \"tags\": [\"x_refsource_MISC\"]}], \"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.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-405\", \"description\": \"CWE-405: Asymmetric Resource Consumption (Amplification)\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2025-12-04T22:04:41.637Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2025-66506\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-12-05T15:32:25.591Z\", \"dateReserved\": \"2025-12-03T15:12:22.978Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2025-12-04T22:04:41.637Z\", \"assignerShortName\": \"GitHub_M\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

RHSA-2026:51033

Vulnerability from csaf_redhat - Published: 2026-08-06 07:31 - Updated: 2026-09-17 15:11

Summary

Red Hat Security Advisory: Red Hat OpenShift API for Data Protection

Severity

Important

Scope

32 vulnerabilities in this advisory, including CVE-2025-66506.

CVE-2025-66506

A flaw was found in Fulcio, a free-to-use certificate authority. This vulnerability allows a denial of service (DoS) due to excessive memory allocation when processing a malicious OpenID Connect (OIDC) identity token containing numerous period characters.

7.5 (High)


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

Fixed: 8 products Known not affected: 37 products

https://access.redhat.com/errata/RHSA-2026:51033

Open the full advisory

RHSA-2026:6166

Vulnerability from csaf_redhat - Published: 2026-03-30 10:40 - Updated: 2026-09-17 13:04

Summary

Red Hat Security Advisory: Red Hat OpenShift Pipelines Release 1.21.1

Severity

Important

Scope

3 vulnerabilities in this advisory, including CVE-2025-66506.

CVE-2025-66506

7.5 (High)


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

Fixed: 4 products Known not affected: 140 products

https://access.redhat.com/errata/RHSA-2026:6166

Open the full advisory

RHSA-2026:6170

Vulnerability from csaf_redhat - Published: 2026-03-30 12:14 - Updated: 2026-09-17 13:04

Summary

Red Hat Security Advisory: Red Hat OpenShift Pipelines Release 1.21.1

Severity

Important

Scope

4 vulnerabilities in this advisory, including CVE-2025-66506.

CVE-2025-66506

7.5 (High)


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

Fixed: 1 product

https://access.redhat.com/errata/RHSA-2026:6170

Open the full advisory

ubuntu-cve-2025-66506

Vulnerability from osv_ubuntu

Published

2025-12-04 22:15

Modified

2026-05-20 15:22

Summary

Details

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"
  ]
}

WID-SEC-W-2026-0199

Vulnerability from csaf_certbund - Published: 2026-01-22 23:00 - Updated: 2026-08-05 22:00

Summary

Red Hat OpenShift Pipelines Operator (Fulcio): Schwachstelle ermöglicht Denial of Service

Severity

Mittel

Scope

1 vulnerability in this advisory, including CVE-2025-66506.

CVE-2025-66506

Known affected: 2 products

Open the full advisory

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

Related by attack behaviour

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.

Action not permitted

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

RHSA-2026:51033

RHSA-2026:6166

RHSA-2026:6170

ubuntu-cve-2025-66506

Vulnerability from osv_ubuntu

WID-SEC-W-2026-0199

Tags

Sightings

Nomenclature

Related by attack behaviour