Cyber Resilience

CVE-2026-27125

Svelte ≤ 5.51.5

Published
20 February 2026
Modified
23 February 2026
Patch / advisory
View advisory
CVSS Score v4 5.3
Click a component to see what it means
Raw vectorCVSS: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
EPSS Score 0.0038 31th percentile
Risk Priority 26 floored blend · peak EPSS

Summary

CVE-2026-27125 is a medium-severity Improperly Controlled Modification of Dynamically-Determined Object Attributes (CWE-915) vulnerability in Svelte Svelte. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 31th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and AC-6 (Least Privilege) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A08:2025 Software or Data Integrity Failures

EU & UK References

Vulnerability Data

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 —…

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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.

CWE(s)
CWE-915

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1098 Account Manipulation Persistence
Adversaries may manipulate accounts to maintain and/or elevate access to victim systems.
attack.mitre.org →
T1098.001 Additional Cloud Credentials Persistence
Adversaries may add adversary-controlled credentials to a cloud account to maintain persistent access to victim accounts and instances within the environment.
attack.mitre.org →
T1098.003 Additional Cloud Roles Persistence
An adversary may add additional roles or permissions to an adversary-controlled cloud account to maintain persistent access to a tenant.
attack.mitre.org →
T1098.004 SSH Authorized Keys Persistence
Adversaries may modify the SSH <code>authorized_keys</code> file to maintain persistence on a victim host.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-42599Same product: Svelte Svelte
CVE-2026-27121Same product: Svelte Svelte
CVE-2026-27902Same product: Svelte Svelte
CVE-2026-27901Same product: Svelte Svelte
CVE-2025-15265Same product: Svelte Svelte
CVE-2026-27122Same product: Svelte Svelte
CVE-2024-45047Same product: Svelte Svelte
CVE-2026-27119Same product: Svelte Svelte
CVE-2026-42573Same product: Svelte Svelte
CVE-2026-42567Same product: Svelte Svelte

Affected Assets

svelte
svelte
≤ 5.51.5

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

AC-3 Access Enforcement good match

Enforces authorizations so that only permitted attributes may be modified on an object.

AC-6 Least Privilege good match

Limits the set of modifiable attributes a subject is authorized to touch.

SI-10 Information Input Validation good match

Validates incoming attribute names and values so that only explicitly allowed fields are accepted for update.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require allow-listing of mutable object attributes and input validation to block mass-assignment flaws.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.28 Secure coding mostly match
prevents

Secure coding standards explicitly forbid unsafe dynamic attribute assignment and require property allow-lists.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect mass-assignment flaws but does not itself prevent them at runtime.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle requires input validation and object-property whitelisting that directly mitigates mass-assignment risks.

A.8.26 Application security requirements partial match
prevents

Application security requirements include explicit rules for allowable object attributes and safe deserialization.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles mandate strict control over dynamic object modification and attribute binding.

A.8.3 Information access restriction partial match
prevents

Information access restriction limits who can modify objects but does not address which attributes may be changed.

References