CVE-2026-45028 — astro
Fix: withastro/astro@3d82220CVE-2026-45028 is a CWE-323 vulnerability in astro. A fix is available for astro — see the affected versions and patch details below.
Astro: Server island encrypted parameters vulnerable to cross-component replay
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2026-45028.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
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.
astronpmDescription
Impact
Astro versions prior to 6.1.10 used AES-GCM encryption to protect the confidentiality and integrity of server island props and slots parameters, but did not bind the ciphertext to its intended component or parameter type. An attacker could replay one component's encrypted props (p) value as another component's slots (s) value, or vice versa.
Since slots contain raw unescaped HTML while props may contain user-controlled values, this could lead to XSS in applications that meet all of the following conditions:
- The application uses server islands
- Two different server island components share the same key name for a prop and a slot
- An attacker has full control over the value of the overlapping prop (requires a dynamically rendered page)
These conditions are very unlikely to occur in real-world production applications.
Patches
This has been patched in [email protected].
The fix binds each encrypted parameter to its target component and purpose using AES-GCM authenticated additional data (AAD). Each ciphertext now includes context like props:IslandName or slots:IslandName, so encrypted data for one component cannot be replayed against a different component, and encrypted props cannot be reused as slots.
References
- Fix PR: https://github.com/withastro/astro/pull/16457
- Example demonstrating the vulnerability: https://github.com/CyberSecurityAustria/ACSC2026-web-astronomical
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | astro | all versions | 6.1.10npm install astro@6.1.10 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for astro, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update astro to 6.1.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45028 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-45028 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-45028. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-45028 in your dependencies?
O3 Security finds CVE-2026-45028 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.