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Fencer Vulns
high 7.5

CVE-2025-66506 json

Fulcio allocates excessive memory during token parsing

published 2025-12-04 11 mo ago modified 2026-10-18 22 d ago also EUVD-2025-201293 , GHSA-f83f-xpx7-ffpw , GO-2025-4193

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 13%
public exploits
0
none known

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.

Patch / fix

  • go github.com/sigstore/fulcio 1.8.3
  • linuxfoundation fulcio 1.8.3
  • golang-github-sigstore-fulcio Debian 14 1.8.5-1

debian advisories DEBIAN-CVE-2025-66506

  • govulncheck-vulndb SLE Module for Package Hub 15 SP6, openSUSE Leap 15.6 0.0.20251209T172047-150000.1.127.1

suse advisories SUSE-SU-2025:4395-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-66506 updated cvss 7.5

github.com/sigstore/fulcio: Fulcio: Denial of Service via crafted OpenID Connect (OIDC) token

  • Red Hat Assisted Installer for Red Hat OpenShift Container Platform 2 rhai/assisted-installer-controller-rhel9
    affected: no fix available
  • Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/cluster-logging-rhel9-operator Red Hat Migration Toolkit for Virtualization mtv-candidate/mtv-must-gather-rhel8, migration-toolkit-virtualization/mtv-must-gather-rhel8
    affected: no fix planned “Will not fix”
  • Red Hat Multiarch Tuning Operator multiarch-tuning/multiarch-tuning-rhel9-operator, multiarch-tuning/multiarch-tuning-operator-bundle Red Hat Multicluster Engine for Kubernetes multicluster-engine/assisted-installer-controller-rhel9 Red Hat OpenShift API for Data Protection oadp/oadp-velero-plugin-rhel8 Red Hat OpenShift Developer Tools and Services openshift4/ose-jenkins, ocp-tools-4/jenkins-rhel8, ocp-tools-4/jenkins-rhel9, ocp-tools-4/jenkins-agent-base-rhel9
    affected: no fix available
  • Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-service-api-rhel9, openshift-lightspeed-tech-preview/lightspeed-rag-tool-rhel9
    affected: no fix planned “Will not fix”
  • Red Hat OpenShift Pipelines openshift-pipelines-client, openshift-pipelines/pipelines-opc-rhel9, openshift-pipelines/pipelines-cli-tkn-rhel8, openshift-pipelines/pipelines-rhel9-operator, openshift-pipelines/pipelines-operator-proxy-rhel9, openshift-pipelines/pipelines-operator-webhook-rhel8, +1 more Red Hat OpenShift Serverless openshift-serverless-1/kn-plugin-event-sender-rhel9, openshift-serverless-1/serverless-must-gather-rhel9
    affected: no fix available, no fix planned “Will not fix”
  • Red Hat Advanced Cluster Security 4 advanced-cluster-security/rhacs-operator-bundle Red Hat AI Inference Server rhaiis/vllm-spyre-rhel9 Red Hat Certification Program for Red Hat Enterprise Linux 9 rhcertification/redhat-certification-baremetal
    affected: no fix available
  • Red Hat Enterprise Linux 9 rhel9-eus/rhel-9.6-bootc-image-builder Red Hat Enterprise Linux 10 rhel10-eus/rhel-10.0-bootc-image-builder Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9
    affected: no fix planned “Will not fix”
  • Red Hat OpenShift Container Platform 4 openshift4/cnf-tests-rhel8, openshift4/cnf-tests-rhel9, openshift4/ose-must-gather-rhel9, openshift4/ptp-must-gather-rhel9, openshift4/microshift-bootc-rhel9, openshift4/ose-local-storage-mustgather-rhel9, +3 more Red Hat OpenShift GitOps openshift-gitops-1/must-gather-rhel8 Red Hat Quay 3 quay/quay-builder-rhel8
    affected: no fix available
show 21 more
  • Red Hat Network Observability (NETOBSERV) 1.11.0 network-observability 1771226060
    fixed: vendor fix RHSA-2026:2900
  • Red Hat OpenShift API for Data Protection 1.3 oadp/oadp-mustgather-rhel9 1785177359, oadp/oadp-velero-plugin-rhel9 1785177357
    fixed: vendor fix RHSA-2026:51033
  • Red Hat OpenShift Security Profiles Operator 1 compliance 1770869850, compliance 1771367226
    fixed: vendor fix RHSA-2026:2852
  • Red Hat Advanced Cluster Security 4.8 advanced-cluster-security 1769615659
    fixed: vendor fix RHSA-2026:1517
  • Red Hat Advanced Cluster Security 4.9 advanced-cluster-security 1770074713, advanced-cluster-security 1770250889
    fixed: vendor fix RHSA-2026:2350
  • Red Hat AI Inference Server 3.2 rhaiis 1772160593, rhaiis 1772160625, rhaiis 3.2.5-1765361180, rhaiis 3.2.5-1765361184, rhaiis 3.2.5-1765552580, rhaiis 3.2.5-1765552603, +1 more
    fixed: vendor fix RHSA-2025:23202
  • Red Hat Migration Toolkit 1.8 rhmtc/openshift-migration-controller-rhel8 1783953372
    fixed: vendor fix RHSA-2026:41928
  • Red Hat OpenShift AI 2.25 rhoai 1770053703, rhoai 1770053721, rhoai 1770053723, rhoai 1770053728, rhoai 1770053730, rhoai 1770053733, +19 more
    fixed: vendor fix RHSA-2026:2106
  • Red Hat OpenShift AI 3.3 rhoai 1769162595, rhoai 1770788873, rhoai 1771415661, rhoai 1771502843, rhoai 1771502844, rhoai 1771502845, +13 more
    fixed: vendor fix RHSA-2026:3713
  • Red Hat Openshift Data Foundation 4.22 odf4/cephcsi-rhel9 1782932114, odf4/odf-cli-rhel9 1783537001, odf4/mcg-core-rhel9 1783536000, odf4/odf-drbd-rhel9 1783537392, odf4/odf-console-rhel9 1783537586, odf4/devicefinder-rhel9 1782932104, +21 more
    fixed: vendor fix RHSA-2026:37387
  • Red Hat OpenShift Pipelines 1.15 openshift-pipelines 1772093872, openshift-pipelines 1772122754, openshift-pipelines 1772613829
    fixed: vendor fix RHSA-2026:3710
  • Red Hat OpenShift Pipelines 1.20 openshift-pipelines 1771374749, openshift-pipelines 1772694865
    fixed: vendor fix RHSA-2026:3825
  • Red Hat OpenShift Pipelines 1.21 openshift-pipelines 1769115266, openshift-pipelines 1774262633, openshift-pipelines 1774871390
    fixed: vendor fix RHSA-2026:6166
  • Red Hat Quay 3.9 quay 1770856103
    fixed: vendor fix RHSA-2026:2754
  • Red Hat Quay 3.10 quay 1770249183
    fixed: vendor fix RHSA-2026:2762
  • Red Hat Quay 3.12 quay 1769852013
    fixed: vendor fix RHSA-2026:1730
  • Red Hat Quay 3.13 quay 1773088862
    fixed: vendor fix RHSA-2026:4185
  • Red Hat Quay 3.14 quay 1773097621
    fixed: vendor fix RHSA-2026:4215
  • Red Hat Quay 3.15 quay 1770146565
    fixed: vendor fix RHSA-2026:1942
  • Red Hat Trusted Artifact Signer 1.2 rhtas 1770733887, rhtas 1770734283, rhtas 1770789792
    fixed: vendor fix RHSA-2026:2924
  • Red Hat Trusted Artifact Signer 1.3 rhtas 1770107446, rhtas 1770107585, rhtas 1770108193
    fixed: vendor fix RHSA-2026:2136

45 more not affected in the full advisory

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
11 mo ago

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
go github.com/sigstore/fulcio
<1.8.3
1.8.3

Affected products

  • sigstore fulcio

Classification

Weakness
  • CWE-405 Asymmetric Resource Consumption (Amplification)

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.