CVE-2026-128122sveltejs kit cross-site scripting
CVE-2026-128122 is a cross-site scripting in sveltejs kit, rated medium (5.9 on CVSS 3.1).
Why this priority: Medium severity, with no exploitation signal.
Published · Updated · NVD status: Received
What it is
Input is written into a web page without escaping, so an attacker's script runs in the browser of anyone who views it. Line breaks in input end up in headers or logs, letting an attacker add lines of their own.
How it is reached
An attacker can exploit it over the network, without an account, and nobody has to click anything. Success also depends on conditions the attacker does not fully control.
What an attacker gains
A successful attack can read the data it protects. In practice, this kind of flaw lets an attacker act inside a signed-in user's browser session.
Is it being exploited?
There is no public report of exploitation yet.
What to do
- Upgrade sveltejs kit to a fixed version for your release line (7.2.10, 8.0.2).
- Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
Description from NVD
SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. From version 4.7.0 until versions 7.2.10 and 8.0.2, @sveltejs/adapter-cloudflare allowed an attacker-influenced link crawled during prerendering to place whitespace, control characters, wildcards, or placeholders into a prerendered redirect path. The adapter wrote those paths into the Cloudflare _redirects output without output-context validation, allowing a path to create unintended routing rules that could redirect or expose requests beyond the intended prerendered route. This issue is fixed in 7.2.10 and 8.0.2.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Web front ends and single-page apps. The flaw sits between a user's browser and the web application.
- Admin consoles served to a browser. The flaw sits between a user's browser and the web application.
- Proxies, load balancers and the servers behind them. The flaw sits between a front-end proxy and its back end.
Trust boundaries in play
- Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
- Between a user's browser and the web application. An attacker who crosses it can act inside a signed-in user's browser session.
- Between a front-end proxy and its back end. An attacker who crosses it can smuggle requests past the proxy's checks.
Questions to answer about your own systems
- Where does sveltejs kit run in your systems, and at which version?
- Which of those instances can be reached from the internet or partner networks?
- What can it reach once compromised: which data stores, secrets and services?
Read more
Patches and commits
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.