How severe is CVE-2026-59711?

No CVSS score has been assigned to CVE-2026-59711 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-59711?

CVE-2026-59711 affects the following packages: showdown (npm). Ecosystems affected: npm.

How do I fix CVE-2026-59711?

No patched version of showdown has shipped for CVE-2026-59711 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

How do I detect CVE-2026-59711 in my npm dependencies?

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

How do I mitigate CVE-2026-59711 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-2026-59711 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-59711 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-2026-59711?

CVE-2026-59711 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 23th 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-2026-59711?

CVE-2026-59711 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-2026-59711 published, and has it been updated?

CVE-2026-59711 was published on July 6, 2026 and was last updated on August 19, 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

CVE-2026-59711 — showdown

Fix: showdownjs/showdown@184a3e4

CVE-2026-59711 is a Cross-site Scripting (XSS) vulnerability in showdown. No vendor fix is recorded yet; mitigation options are listed below.

showdown - Cross-Site Scripting via Unescaped Metadata Title in completeHTMLDocument

Also known asGHSA-cr32-g25g-vxjj

Published

Jul 6, 2026

Updated

Aug 19, 2026

Affected

1 pkg

Patched

See advisory

Exploits

None indexed

Exploitation data as of Oct 2, 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.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-59711.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs23th percentile — riskier than 23% of all scored CVEsHighest risk

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

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.

1Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

showdownnpm

1.6Mdownloads / week

Description

showdown contains a cross-site scripting vulnerability in metadata title handling that allows attackers to inject arbitrary HTML and JavaScript. When completeHTMLDocument option is enabled, unescaped less-than and greater-than characters in markdown frontmatter metadata are inserted directly into HTML title tags, enabling attackers to break out of the title context and execute malicious scripts in the rendered page.

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
📦npm	`showdown`	all versions	No fix

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for showdown, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of showdown has shipped for CVE-2026-59711 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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

Red Hat rates this flaw as Moderate. Exploitation requires two non-default showdown options enabled simultaneously: metadata and completeHTMLDocument, both of which default to false. Red Hat products that ship showdown do not enable completeHTMLDocument in their default configurations, which reduces the likelihood of…

Workaround published by Red Hat

Do not enable showdown's completeHTMLDocument option when processing untrusted markdown input. If the option is required, sanitize metadata values before passing them to the converter.

Source: Red Hat security advisory for CVE-2026-59711 (CC BY 4.0)

Frequently Asked Questions

O3 Security · Impact-Aware SCA

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