How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

362,557

Total vulnerabilities in the database

CVE-2026-59727 — @sentry / astro

Improper Encoding or Escaping of Output

Summary

When a transition:persist, transition:scope, or transition:persist-props directive is applied to a client-hydrated (client:*) component, Astro copied the directive value onto the rendered <astro-island> element without HTML-escaping it. If a developer reflects attacker-controlled input into one of these directives, an attacker can break out of the attribute and inject arbitrary HTML/JavaScript into the server-rendered output, resulting in reflected cross-site scripting (XSS).

Severity

Although a generic reflected XSS scores in the Medium range, exploitation here requires the application developer to have written a non-idiomatic pattern — passing untrusted, request-derived input directly into a transition directive. Astro applications that do not route untrusted input into these directives are unaffected. This mitigating precondition places the real-world severity at Low.

Details

In generateHydrateScript() (packages/astro/src/runtime/server/hydration.ts), every island property is HTML-escaped before serialization — the attrs, props, and opts assignments all pass through escapeHTML(). The transition directives, however, were copied verbatim:

transitionDirectivesToCopyOnIsland.forEach((name) =&gt; {
  if (typeof props[name] !== &#039;undefined&#039;) {
    island.props[name] = props[name]; // not escaped
  }
});

The <astro-island> element is serialized via renderElement('astro-island', island, false) with shouldEscape=false, and toAttributeString() returns the value unchanged in that mode. As a result there is no downstream re-escaping, and the raw directive value reaches the HTML response. This is the same output sink previously addressed for slot names in GHSA-8hv8-536x-4wqp.

The affected directives are:

data-astro-transition-scope (transition:scope)
data-astro-transition-persist (transition:persist)
data-astro-transition-persist-props (transition:persist-props)

Note that transition:persist is typed boolean | string, so passing a string value is a supported use of the API.

Proof of Concept

A component that reflects a query parameter into a transition directive:

---
const persist = Astro.url.searchParams.get(&#039;persist&#039;) ?? &#039;default&#039;;
---
&lt;Island client:load transition:persist={persist} /&gt;

Request:

https://example.com/?persist=&quot;&gt;&lt;img src=x onerror=alert(document.domain)&gt;

Rendered output (before the fix):

&lt;astro-island … data-astro-transition-persist=&quot;&quot;&gt;&lt;img src=x onerror=alert(document.domain)&gt;&gt;&lt;/astro-island&gt;

The " closes the attribute and the injected <img onerror=…> executes in the victim's browser.

Impact

Reflected XSS. An attacker who can induce a victim to visit a crafted URL can execute arbitrary script in the victim's session on the origin, subject to the requirement that the target application reflects untrusted input into one of the affected transition directives.

Affected Versions

astro >= 3.10.0, < 7.0.4 (introduced in 3.10.0, PR #7861).

Patched Versions

astro >= 7.0.4. Fixed in PR #17212 by HTML-escaping transition directive values before they are rendered onto the island element.

Workarounds

Do not pass untrusted or request-derived input into transition:persist, transition:scope, or transition:persist-props. If such input is required, HTML-escape or strictly validate it before passing it to the directive. Upgrading to [email protected] or later removes the need for manual mitigation.

Credits

Reported by @jlgore.

Published: Jul 20, 2026
Updated: Jul 21, 2026
CVE: CVE-2026-59727
GHSA: GHSA-7pw4-f3q4-r2p2
Severity: Low
Exploit:
CISA KEV:

No technical information available.

CWEs:

OWASP TOP 10:

A7 - Cross-Site Scripting (XSS)

Affected Software
References

Software	From	Fixed in
@sentry / astro	3.10.0	7.0.4

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.