How severe is CVE-2023-26364?

CVE-2023-26364 has a CVSS score of 5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-26364?

CVE-2023-26364 affects the following packages: @adobe/css-tools (npm). Ecosystems affected: npm.

How do I fix CVE-2023-26364?

Update @adobe/css-tools to 4.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-26364 is resolved across your whole dependency graph.

How do I detect CVE-2023-26364 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @adobe/css-tools, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2023-26364 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2023-26364 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-26364 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-26364?

CVE-2023-26364 has an EPSS (Exploit Prediction Scoring System) score of 1.2%, placing it in the 67th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-26364?

CVE-2023-26364 is classified as Improper Input Validation (CWE-20). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2023-26364 published, and has it been updated?

CVE-2023-26364 was published on August 29, 2023 and was last updated on May 4, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

CVE-2023-26364 — @adobe/css-tools

MEDIUMFix: adobe/css-tools@2b09a25

CVE-2023-26364 is a medium-severity (CVSS 5) Improper Input Validation vulnerability in @adobe/css-tools. A fix is available for @adobe/css-tools — see the affected versions and patch details below.

@adobe/css-tools Regular Expression Denial of Service (ReDOS) while Parsing CSS

Published

Aug 29, 2023

Updated

May 4, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2023-26364.

EPSS Exploitation Probability

via FIRST.org ↗

1.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs67th percentile — riskier than 67% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

66other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@adobe/css-toolsnpm

83.5Mdownloads / week

Description

Impact

@adobe/css-tools version 4.3.0 and earlier are affected by an Improper Input Validation vulnerability that could result in a denial of service while attempting to parse CSS.

Patches

The issue has been resolved in 4.3.1.

Workarounds

None

References

N/A

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@adobe/css-tools`	all versions	4.3.1`npm install @adobe/css-tools@4.3.1`

Affected Products

1 product · 1 configurations

Application

css-toolsadobe

< 4.3.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @adobe/css-tools, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @adobe/css-tools to 4.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-26364 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Workaround published by Red Hat

No mitigation is yet available for this vulnerability.

Source: Red Hat security advisory for CVE-2023-26364 (CC BY 4.0)

Product	Fixed in	Advisory
Migration Toolkit for Runtimes 1 on RHEL 8	`mtr/mtr-operator-bundle:1.2-23`	RHSA-2024:3919
MTA-6.2-RHEL-9	`mta/mta-windup-addon-rhel9:6.2.3-2`	RHSA-2024:3989
MTA-7.0-RHEL-9	`mta/mta-cli-rhel9:7.0.3-16`	RHSA-2024:3316
RHODF-4.14-RHEL-9	`odf4/odf-multicluster-console-rhel9:v4.14.13-3`	RHSA-2025:0323
RHODF-4.15-RHEL-9	`odf4/odf-multicluster-console-rhel9:v4.15.9-1`	RHSA-2025:0164
RHODF-4.16-RHEL-9	`odf4/odf-multicluster-console-rhel9:v4.16.5-2`	RHSA-2025:0082
RHODF-4.17-RHEL-9	`odf4/odf-multicluster-console-rhel9:v4.17.0-53`	RHSA-2024:8676

Frequently Asked Questions

### Impact @adobe/css-tools version 4.3.0 and earlier are affected by an Improper Input Validation vulnerability that could result in a denial of service while attempting to parse CSS. ### Patches The issue has been resolved in 4.3.1. ### Workarounds None ### References N/A