Quick answers
- Is CVE-2026-27122 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-27122 being exploited in the wild.
- How severe is CVE-2026-27122?
- Medium severity, with a CVSS score of 4, published 19 February 2026.
- Which products and versions are affected?
- svelte (npm) SEMVER:introduced=0,fixed=5.51.5.
- Is there a fix for CVE-2026-27122?
- Yes. svelte (npm): upgrade to 5.51.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-27122 attacked?
- It is attacked over the network.
- Am I affected by CVE-2026-27122?
- Check whether you run svelte (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- svelte (npm): upgrade to 5.51.5 or later
npm install svelte@5.51.5
Technical details
The vulnerability is an HTML injection flaw (CWE-79) in Svelte's server-side rendering engine. When the `<svelte:element this={tag}>` component is used with a user-controlled or attacker-supplied tag name, the tag value is not validated before being emitted into the HTML output, allowing special characters and HTML markup to be injected. Client-side rendering is not affected. The attack requires network access and high privileges (an attacker must be able to provide input that influences the tag parameter). This can lead to HTML injection in SSR output with potential impact on confidentiality and integrity of subsequent systems. The vulnerability affects Svelte versions up to and including 5.51.4, and is patched in version 5.51.5 and later.
Affected products
- Svelte Svelte <=5.51.4
Identifiers
- CVE-2026-27122
- GHSA-m56q-vw4c-c2cp
Timeline
- 2026-02-19: disclosed: GHSA-m56q-vw4c-c2cp published
- 2026-02-19: patched: Fixed in version 5.51.5
- 2026-02-20: other: CVE-2026-27122 published on NVD