CVE-2026-30226Network attack vector

Service interruption via unchecked __proto__ hydration

Published Mar 11, 2026 · Updated Mar 11, 2026

Prototype pollution in Svelte devalue before 5.6.4 allows remote attackers to interrupt services via crafted serialized data. The Object-wrapper and null-prototype paths in parse and unflatten hydrate attacker-supplied proto keys instead of rejecting them. A consuming application must pass attacker-controlled data to either API; exploitation causes denial of service or type confusion.

CVSS severity6.3
Medium
EPSS probability0.37%
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 Svelte devalue before 5.6.4 allows remote attackers to interrupt services via crafted serialized data. The Object-wrapper and null-prototype paths in parse and unflatten hydrate attacker-supplied proto keys instead of rejecting them. A consuming application must pass attacker-controlled data to either API; exploitation causes denial of service or type confusion.

The record

CVE
CVE-2026-30226
Published
Mar 11, 2026
Updated
Mar 11, 2026
Vendor
Svelte
Product
devalue
Classifications
CWE-1321
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 11, 2026Record 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=< 5.6.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Svelte · devalueversion=< 5.6.4

Published CVSS scores

6.3GitHub, Inc.CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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