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Fencer Vulns
medium 4.3

CVE-2026-9358 json

postcss-selector-parser AST Serialization container.js toString recursion

published 2026-05-24 5 mo ago modified 2026-09-10 1 mo ago also GHSA-w9m9-85wc-3x92 , EUVD-2026-31571

cvss
4.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

A vulnerability was determined in postcss-selector-parser up to 6.1.2/7.1.2. Affected is the function toString of the file src/selectors/container.js of the component AST Serialization. Executing a manipulation can lead to uncontrolled recursion. It is possible to launch the attack remotely. The exploit has been publicly disclosed and may be utilized. Upgrading to version 6.1.3 and 7.1.3 is able to address this issue. This patch is called 5bc698cef66f8abd12610dc623e5d67cbc0f869d. It is suggested to upgrade the affected component. The vendor explains, that according to his definition "DoS on server-side on user-generated CSS is low risk for us (since most users compile own CSS with PostCSS)." The commits were backported to 6.x branch, which was the most downloaded version.

Patch / fix

  • npm postcss-selector-parser 6.1.3, 7.1.3
  • n/a postcss-selector-parser 6.1.3, 7.1.3
  • node-css-loader Debian 14 6.8.1+~cs14.1.4-1

debian advisories DEBIAN-CVE-2026-9358

  • rust hummingbird 1 1.96.0-1.hum1
  • cargo hummingbird 1 1.96.0-1.hum1
  • clippy hummingbird 1 1.96.0-1.hum1
  • rustfmt hummingbird 1 1.96.0-1.hum1
  • rust-gdb hummingbird 1 1.96.0-1.hum1
  • rust-src hummingbird 1 1.96.0-1.hum1
  • rust-lldb hummingbird 1 1.96.0-1.hum1
  • rust-analyzer hummingbird 1 1.96.0-1.hum1

red hat advisories RHSA-2026:22934

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-2026-9358 updated cvss 4.3

postcss-selector-parser: Postcss: Denial of Service via uncontrolled recursion in AST Serialization

  • Red Hat Cryostat 4 postcss, postcss-selector-parser, cryostat-openshift-console-plugin-npm Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9 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
    +34 more products
    Red Hat Node HealthCheck Operator workload-availability/node-healthcheck-rhel9-operator, workload-availability/node-healthcheck-operator-bundle, workload-availability/node-healthcheck-must-gather-rhel9 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 AMQ Broker 7 postcss, postcss-selector-parser Red Hat Ansible Automation Platform 2 automation-gateway, automation-platform-ui, automation-eda-controller, ansible-automation-platform-26/gateway-rhel9, ansible-automation-platform-27/gateway-rhel9 Red Hat build of Apache Camel - HawtIO 4 postcss, postcss-selector-parser Red Hat build of Apache Camel for Spring Boot 4 postcss, postcss-selector-parser 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 Keycloak postcss 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, postcss-selector-parser Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat Discovery 2 discovery/discovery-ui-rhel9 Red Hat Enterprise Linux 7 firefox, rhsm-gtk, python-syspurpose, subscription-manager, subscription-manager-gui, subscription-manager-rhsm, +6 more Red Hat Enterprise Linux 8 pcs, firefox, mozjs60, pcs-snmp, rhsm-gtk, rhsm-icons, +12 more Red Hat Enterprise Linux 9 gjs, pcs, goose, firefox, grafana, pcs-snmp, +3 more Red Hat Enterprise Linux 10 goose, firefox, grafana, thunderbird Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/disk-image-cuda-rhel9 Red Hat Fuse 7 postcss, postcss-selector-parser Red Hat JBoss Enterprise Application Platform 7 postcss, postcss-selector-parser 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, rhoai/odh-dashboard-rhel9, rhoai/odh-mod-arch-maas-rhel9, rhoai/odh-mod-arch-automl-rhel9, rhoai/odh-mod-arch-gen-ai-rhel9, rhoai/odh-mod-arch-mlflow-rhel9, +4 more 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 Container Platform 5 openshift5/ose-console-rhel9 Red Hat Openshift Data Foundation 4 odf4/odf-console-rhel8, odf4/odf-multicluster-console-rhel8 Red Hat OpenShift Dev Spaces devspaces/openvsx-rhel9, devspaces/dashboard-rhel9
    affected: workaround, no fix available “Upgrade to PostCSS 8.5.6 or later. As a workaround, validate and sanitize CSS input before processing with PostCSS to prevent deeply nested or malicious structures from reaching the serializer.”

9 more affected, 3 more fixed, 6 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
5 mo ago

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • gist.github.com https://gist.github.com/bx33661/581e3a38134601c04e19b4dfc9b459b9 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 5.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
CNA 3.0 4.3 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
CNA 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C
CNA 4.0 2.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CNA 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
CNA 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub 3.1 4.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Affected packages

ecosystem package affected fixed in
npm postcss-selector-parser
>=6.1.0, <6.1.3
>=7.1.0, <7.1.3
6.1.3
7.1.3

Affected products

  • n/a postcss-selector-parser

Classification

Weakness
  • CWE-674 Uncontrolled Recursion
  • CWE-404 Improper Resource Shutdown or Release

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.