CVE-2026-27121
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.
- Record
CVE-2026-27121- CVSS 4.0
- 5.1 Medium
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N - Weakness
- CWE-79
- Updated
- 2026-11-02
EUVDEUVD-2026-7521
svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.
- Record
EUVD-2026-7521- CVSS 4.0
- 5.1 Medium
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-f7gr-6p89-r883
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers.
- Record
GHSA-f7gr-6p89-r883- CVSS 4.0
- 5.1 Medium
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N - Weakness
- CWE-79
- Updated
- 2026-11-02
NVD
svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.
- Record
CVE-2026-27121- CVSS 4.0
- 5.1 Medium
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.
- Record
CVE-2026-27121- CVSS 4.0
- 5.1 Medium
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSVGHSA-f7gr-6p89-r883
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers.
- Record
GHSA-f7gr-6p89-r883- CVSS 4.0
- 5.1 Medium
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N - Weakness
- CWE-79
- Updated
- 2026-11-02
Show 5 moreShow less
OSVCLSA-2026-1775953999 No score
TuxCare security update for svelte (4 CVEs)
TuxCare rebuilt svelte to address 4 CVEs. Fixed in 4.2.20-tuxcare.1.
- Record
CLSA-2026-1775953999- Updated
- 2026-11-02
OSVCLSA-2026-1776040402 No score
TuxCare security update for svelte (5 CVEs)
TuxCare rebuilt svelte to address 5 CVEs. Fixed in 3.59.2-tuxcare.1.
- Record
CLSA-2026-1776040402- Updated
- 2026-11-02
OSVCLSA-2026-1776126838 No score
TuxCare security update for svelte (6 CVEs)
TuxCare rebuilt svelte to address 6 CVEs. Fixed in 2.16.1-tuxcare.1.
- Record
CLSA-2026-1776126838- Updated
- 2026-11-02
OSVCLSA-2026-1776213244 No score
TuxCare security update for svelte (6 CVEs)
TuxCare rebuilt svelte to address 6 CVEs. Fixed in 1.64.1-tuxcare.1.
- Record
CLSA-2026-1776213244- Updated
- 2026-11-02
OSVCLSA-2026-1776213252 No score
TuxCare security update for svelte (6 CVEs)
TuxCare rebuilt svelte to address 6 CVEs. Fixed in 0.3.0-tuxcare.1.
- Record
CLSA-2026-1776213252- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
sveltenpm |
through 5.51.4 | 5.51.5 |
svelteTuxCare:npm From an advisory covering 4 CVEs |
4.2.20-tuxcare.0 up to 4.2.20-tuxcare.1, plus listed versions 4.2.20 |
4.2.20-tuxcare.1 |
svelteTuxCare:npm From an advisory covering 5 CVEs |
3.59.2-tuxcare.0 up to 3.59.2-tuxcare.1, plus listed versions 3.59.2 |
3.59.2-tuxcare.1 |
svelteTuxCare:npm From an advisory covering 6 CVEs |
2.16.1-tuxcare.0 up to 2.16.1-tuxcare.1, plus listed versions 2.16.1 |
2.16.1-tuxcare.1 |
svelteTuxCare:npm From an advisory covering 6 CVEs |
1.64.1-tuxcare.0 up to 1.64.1-tuxcare.1, plus listed versions 1.64.1 |
1.64.1-tuxcare.1 |
svelteTuxCare:npm From an advisory covering 6 CVEs |
0.3.0-tuxcare.0 up to 0.3.0-tuxcare.1, plus listed versions 0.3.0 |
0.3.0-tuxcare.1 |
sveltenpm |
before 5.51.5 | 5.51.5 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-27121 is a medium vulnerability (CVSS 5.1) in Svelte, published February 19, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.22%, the 12th percentile. Fixed in svelte 5.51.5.