CVE-2025-62381Public exploitNetwork attack vector

Prototype corruption via unchecked form-data paths

Published Oct 15, 2025 · Updated Oct 15, 2025

Prototype pollution in sveltekit-superforms 2.27.3 and earlier allows remote attackers to corrupt Object.prototype through crafted form data. parseFormData deserializes __superform_json, derives nested paths from file-parameter names, and passes attacker-controlled paths and values to setPaths without blocking prototype keys. A SvelteKit route must call superValidate on attacker-supplied form data with JSON mode in use; pollution can crash the application, cause type confusion, or enable code execution when a suitable downstream gadget exists.

CVSS severity8.3
High
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in sveltekit-superforms 2.27.3 and earlier allows remote attackers to corrupt Object.prototype through crafted form data. parseFormData deserializes __superform_json, derives nested paths from file-parameter names, and passes attacker-controlled paths and values to setPaths without blocking prototype keys. A SvelteKit route must call superValidate on attacker-supplied form data with JSON mode in use; pollution can crash the application, cause type confusion, or enable code execution when a suitable downstream gadget exists.

The record

CVE
CVE-2025-62381
Published
Oct 15, 2025
Updated
Oct 15, 2025
Vendor
Andreas Söderlund
Product
sveltekit-superforms
Classifications
CWE-1321, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.27.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Andreas Söderlund · sveltekit-superformsversion=< 2.27.4

Published CVSS scores

8.3GitHub, Inc.CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/SC:L/SI:L/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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