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CVE-2026-27125

Svelte SSR attribute spreading includes inherited properties from prototype chain

5.3 MediumFix available

svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
None

Exploit likelihood

0.43%Up 0.4 points since Feb 21, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.3

Svelte SSR attribute spreading includes inherited properties from prototype chain

svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

Record
CVE-2026-27125
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
Weakness
CWE-915
Updated
2026-11-02
EUVDEUVD-2026-7765 5.3

svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

Record
EUVD-2026-7765
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-crpf-4hrx-3jrp 5.3

Svelte SSR attribute spreading includes inherited properties from prototype chain

In server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected.

Record
GHSA-crpf-4hrx-3jrp
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
Weakness
CWE-915
Updated
2026-11-02
NVD 5.3

svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

Record
CVE-2026-27125
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/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
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Weakness
CWE-915
Updated
2026-11-02
OSV 5.3

Svelte SSR attribute spreading includes inherited properties from prototype chain

svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

Record
CVE-2026-27125
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
Weakness
CWE-915
Updated
2026-11-02
OSVGHSA-crpf-4hrx-3jrp 5.3

Svelte SSR attribute spreading includes inherited properties from prototype chain

In server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected.

Record
GHSA-crpf-4hrx-3jrp
CVSS 4.0
5.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N
Weakness
CWE-915
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

Affected packages
PackageAffectedFixed
svelte
npm
through 5.51.4
5.51.5
svelte
TuxCare: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
svelte
TuxCare: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
svelte
TuxCare: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
svelte
TuxCare: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
svelte
TuxCare: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
svelte
npm
before 5.51.5
5.51.5

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-27125 is a medium vulnerability (CVSS 5.3) in Svelte, published February 19, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.43%, the 37th percentile. Fixed in svelte 5.51.5.

References

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