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Fencer Vulns
medium 6.1

CVE-2026-41305 json

PostCSS has XSS via Unescaped </style> in its CSS Stringify Output

published 2026-04-24 6 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-25383 , GHSA-qx2v-qp2m-jg93

cvss
6.1
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 10%
public exploits
0
none known

Summary

PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Versions prior to 8.5.10 do not escape `</style>` sequences when stringifying CSS ASTs. When user-submitted CSS is parsed and re-stringified for embedding in HTML `<style>` tags, `</style>` in CSS values breaks out of the style context, enabling XSS. Version 8.5.10 fixes the issue.

Patch / fix

  • npm postcss 8.5.10
  • postcss postcss 8.5.10
  • node-postcss Debian 14 8.5.12+~cs9.3.32-1

debian advisories DEBIAN-CVE-2026-41305

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-2026-41305 updated cvss 6.1

postcss: PostCSS: Cross-Site Scripting (XSS) via improper escaping of style closing tags

  • Red Hat Cryostat 4 postcss, cryostat-openshift-console-plugin-npm Red Hat Gatekeeper 3 gatekeeper/gatekeeper-rhel9 Red Hat Migration Toolkit for Containers rhmtc/openshift-migration-ui-rhel8 Red Hat Multicluster Engine for Kubernetes multicluster-engine/console-mce-rhel9 Red Hat Network Observability Operator network-observability/network-observability-console-plugin-rhel9 Red Hat Node HealthCheck Operator workload-availability/node-healthcheck-rhel9-operator, workload-availability/node-healthcheck-operator-bundle, workload-availability/node-healthcheck-must-gather-rhel9
    +22 more products
    Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-console-plugin-rhel9, openshift-lightspeed/lightspeed-console-plugin-419-rhel9, openshift-lightspeed/lightspeed-console-plugin-pf5-rhel9 Red Hat OpenShift Pipelines openshift-pipelines/pipelines-hub-ui-rhel8, openshift-pipelines/pipelines-hub-ui-rhel9, openshift-pipelines/pipelines-console-plugin-rhel8, openshift-pipelines/pipelines-console-plugin-rhel9 Red Hat OpenShift Service Mesh 2 openshift-service-mesh/kiali-rhel8, openshift-service-mesh/kiali-ossmc-rhel8 Red Hat OpenShift Service Mesh 3 openshift-service-mesh/kiali-rhel9, openshift-service-mesh/kiali-ossmc-rhel9, openshift-service-mesh/kiali-rhel9-operator, openshift-service-mesh/kiali-operator-bundle Red Hat 3scale API Management Platform 2 3scale-amp21/system, 3scale-amp22/system, 3scale-amp2/system-rhel7, 3scale-amp2/system-rhel8, 3scale-amp2/system-rhel9 Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/console-rhel9 Red Hat Ansible Automation Platform 2 automation-gateway, automation-platform-ui, automation-eda-controller, ansible-automation-platform-26/gateway-rhel9 Red Hat build of Apache Camel - HawtIO 4 postcss Red Hat build of Apicurio Registry 2 postcss Red Hat build of Apicurio Registry 3 apicurio/apicurio-registry-ui-rhel8, apicurio/apicurio-registry-ui-rhel9 Red Hat Build of Podman Desktop rh-podman-desktop.git Red Hat Build of Podman Desktop - Tech Preview rhdesktop/rh-podman-desktop-ext-rhel-rhel10, rhdesktop/rh-podman-desktop-ext-bootc-rhel10, rhdesktop/rh-podman-desktop-ext-sandbox-rhel10, rhdesktop/rh-podman-desktop-ext-redhat-account-rhel10, rhdesktop/rh-podman-desktop-ext-openshift-local-rhel10 Red Hat Connectivity Link 1 rhcl-1/rhcl-console-plugin-rhel9 Red Hat Data Grid 8 postcss Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9, rhdh/backstage-community-plugin-catalog-backend-module-scaffolder-relation-processor Red Hat Discovery 2 discovery/discovery-ui-rhel9 Red Hat Enterprise Linux 7 firefox Red Hat Enterprise Linux 8 pcs, firefox, grafana, mozjs60, pcs-snmp, thunderbird, +13 more Red Hat Enterprise Linux 9 gjs, pcs, firefox, grafana, pcs-snmp, firefox-x11, +2 more Red Hat Enterprise Linux 10 firefox, grafana, thunderbird Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/disk-image-cuda-rhel9 Red Hat Fuse 7 postcss
    affected: no fix available “Fix deferred”
  • Red Hat Hardened Images nodejs25
    affected: no fix planned “Will not fix”
  • Red Hat JBoss Enterprise Application Platform 7 postcss Red Hat JBoss Enterprise Application Platform 8 postcss Red Hat JBoss Enterprise Application Platform Expansion Pack postcss Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9 Red Hat OpenShift Container Platform 4 openshift3/ose-console, openshift4/ose-console, openshift4/ose-console-rhel9, openshift4/ose-agent-installer-ui-rhel9 Red Hat Openshift Data Foundation 4 odf4/odf-console-rhel8, odf4/odf-multicluster-console-rhel8
    +5 more products
    Red Hat OpenShift Dev Spaces devspaces/openvsx-rhel9, devspaces/dashboard-rhel9 Red Hat OpenShift Virtualization 4 container-native-virtualization/kubevirt-console-plugin-rhel9 Red Hat Process Automation 7 postcss Red Hat Quay 3 quay/quay-rhel8, quay/quay-rhel9 Red Hat Satellite 6 nodejs-css-loader, nodejs-sanitize-html, satellite/iop-advisor-frontend-rhel9, satellite/iop-vulnerability-frontend-rhel9, satellite/iop-host-inventory-frontend-rhel9
    affected: no fix available “Fix deferred”

5 more affected, 3 more fixed, 4 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
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 10% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/postcss/postcss/security/advisories/GHSA-qx2v-qp2m-jg93 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
GitHub 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm postcss
<8.5.10
8.5.10

Affected products

  • postcss postcss

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

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.