CVE-2025-54793 — astro
Fix: withastro/astro@0567fb7CVE-2025-54793 is a Open Redirect vulnerability in astro. A fix is available for astro — see the affected versions and patch details below.
Astro: Duplicate trailing slash feature can lead to Open Redirects
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-2025-54793.
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
Summary
There is an Open Redirection vulnerability in the trailing slash redirection logic when handling paths with double slashes. This allows an attacker to redirect users to arbitrary external domains by crafting URLs such as https://mydomain.com//malicious-site.com/. This increases the risk of phishing and other social engineering attacks.
This affects Astro >=5.2.0 sites that use on-demand rendering (SSR) with the Node or Cloudflare adapter. It does not affect static sites, or sites deployed to Netlify or Vercel.
Background
Astro performs automatic redirection to the canonical URL, either adding or removing trailing slashes according to the value of the trailingSlash configuration option. It follows the following rules:
- If
trailingSlashis set to"never",https://example.com/page/will redirect tohttps://example.com/page - If
trailingSlashis set to"always",https://example.com/pagewill redirect tohttps://example.com/page/
It also collapses multiple trailing slashes, according to the following rules:
- If
trailingSlashis set to"always"or"ignore"(the default),https://example.com/page//will redirect tohttps://example.com/page/ - If
trailingSlashis set to"never",https://example.com/page//will redirect tohttps://example.com/page
It does this by returning a 301 redirect to the target path. The vulnerability occurs because it uses a relative path for the redirect. To redirect from https://example.com/page to https://example.com/page/, it sending a 301 response with the header Location: /page/. The browser resolves this URL relative to the original page URL and redirects to https://example.com/page/
Details
The vulnerability occurs if the target path starts with //. A request for https://example.com//page will send the header Location: //page/. The browser interprets this as a protocol-relative URL, so instead of redirecting to https://example.com//page/, it will attempt to redirect to https://page/. This is unlikely to resolve, but by crafting a URL in the form https://example.com//target.domain/subpath, it will send the header Location: //target.domain/subpath/, which the browser translates as a redirect to https://target.domain/subpath/. The subpath part is required because otherwise Astro will interpret /target.domain as a file download, which skips trailing slash handling.
This leads to an Open Redirect vulnerability.
The URL needed to trigger the vulnerability varies according to the trailingSlash setting.
- If
trailingSlashis set to"never", a URL in the formhttps://example.com//target.domain/subpath/ - If
trailingSlashis set to"always", a URL in the formhttps://example.com//target.domain/subpath - For any config value, a URL in the form
https://example.com//target.domain/subpath//
Impact
This is classified as an Open Redirection vulnerability (CWE-601). It affects any user who clicks on a specially crafted link pointing to the affected domain. Since the domain appears legitimate, victims may be tricked into trusting the redirected page, leading to possible credential theft, malware distribution, or other phishing-related attacks.
No authentication is required to exploit this vulnerability. Any unauthenticated user can trigger the redirect by clicking a malicious link.
Mitigation
Usrs can test if your site is affected by visiting https://yoursite.com//docs.astro.build/en//. If a user is redirected to the Astro docs then their site is affected and must be updated.
Upgrade to Astro 5.12.8. To mitigate at the network level, block outgoing redirect responses with a Location header value that starts with //.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | astro | ≥ 5.2.0&&< 5.12.8 | 5.12.8npm install astro@5.12.8 |
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 5.12.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-54793 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-2025-54793 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-54793. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
How to detect CVE-2025-54793
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2025-54793 -u https://target- Template
- Astro SSR - Open Redirect
- Severity
- medium
- Impact
- Attackers can redirect users to malicious sites, increasing phishing and social engineering risks.
- Remediation
- Upgrade to version 5.12.8 or later; alternatively, block outgoing redirects with Location headers starting with // at the network level.
Template by ProjectDiscovery nuclei-templates (DhiyaneshDk), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2025-54793 in your dependencies?
O3 Security finds CVE-2025-54793 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.