How severe is CVE-2026-0858?

No CVSS score has been assigned to CVE-2026-0858 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-0858?

CVE-2026-0858 affects the following packages: net.sourceforge.plantuml:plantuml (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-0858?

Update net.sourceforge.plantuml:plantuml to 1.2026.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-0858 is resolved across your whole dependency graph.

How do I detect CVE-2026-0858 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for net.sourceforge.plantuml:plantuml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-0858 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2026-0858 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-0858 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-2026-0858?

CVE-2026-0858 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 27th 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-2026-0858?

CVE-2026-0858 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-0858 published, and has it been updated?

CVE-2026-0858 was published on January 16, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2026-0858 — plantuml

Fix: plantuml/plantuml@6826315

CVE-2026-0858 is a Cross-site Scripting (XSS) vulnerability in net.sourceforge.plantuml:plantuml. A fix is available for net.sourceforge.plantuml:plantuml — see the affected versions and patch details below.

PlantUML is vulnerable to Stored XSS due to insufficient sanitization of interactive attributes in GraphViz diagrams

Also known asGHSA-hrvf-g648-rf3m

Published

Jan 16, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-0858.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs27th percentile — riskier than 27% of all scored CVEsHighest risk

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

Real-World Exposure

1 pkg affected

☕net.sourceforge.plantuml:plantuml

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Versions of the package net.sourceforge.plantuml:plantuml before 1.2026.0 are vulnerable to Stored XSS due to insufficient sanitization of interactive attributes in GraphViz diagrams. As a result, a crafted PlantUML diagram can inject malicious JavaScript into generated SVG output, leading to arbitrary script execution in the context of applications that render the SVG.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`net.sourceforge.plantuml:plantuml`	all versions	1.2026.0`net.sourceforge.plantuml:plantuml:1.2026.0`

Affected Products

1 product · 1 configurations

Application

plantumlplantuml

< 1.2026.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for net.sourceforge.plantuml:plantuml, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update net.sourceforge.plantuml:plantuml to 1.2026.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-0858 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

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

This vulnerability is rated Moderate for Red Hat. It affects PlantUML versions prior to 1.2026.0, allowing Stored Cross-Site Scripting (XSS) through crafted GraphViz diagrams. When a malicious PlantUML diagram is processed, it can inject arbitrary JavaScript into the generated SVG output, which then executes in the…

Workaround published by Red Hat

To mitigate this vulnerability, avoid processing or rendering PlantUML diagrams from untrusted sources. If processing untrusted diagrams is unavoidable, ensure that the environment where the SVG output is rendered is adequately sandboxed to limit the impact of potential script execution. This operational control helps reduce exposure to the Stored XSS flaw.

Source: Red Hat security advisory for CVE-2026-0858 (CC BY 4.0)

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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