November 14, 2026

CVE Watchtower

CVE-2026-123567sveltejs devalue Prototype Pollution

NVD

Vulnerability Summary

Sveltejs devalue before 5.6.4 contains a prototype injection vulnerability that allows attackers to inject __proto__ own properties into objects returned by devalue.parse and devalue.unflatten. Attackers can supply crafted serialized input that, when downstream code merges results via Object.assign, alters the target object's prototype.
Severity Level
MEDIUM(6.3)
Published Date
Nov 8, 2026
Last Modified
Nov 13, 2026
Exploitation Status
No confirmed exploitation yet
EPSS Score (30-Day)
0.24%Probability
Root Weakness (CWE)
CWE-1321: Prototype Pollution ↗
The product receives input that specifies attributes to be initialized or updated in an object, but does not properly control modifications of attributes of the object prototype.
CVSS v4.0 Base Metrics — Score 6.3 (MEDIUM)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Attack VectorNetwork
Attack ComplexityLow
Attack RequirementsPresent
Privileges RequiredNone
User InteractionNone
Confidentiality (Vulnerable System)None
Integrity (Vulnerable System)Low
Availability (Vulnerable System)None
Confidentiality (Subsequent System)None
Integrity (Subsequent System)None
Availability (Subsequent System)None
Show CVSS v3.x metrics (score 3.7)
CVSS v3.1 Base Metrics — Score 3.7 (LOW)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack VectorNetwork
Attack ComplexityHigh
Privileges RequiredNone
User InteractionNone
ScopeUnchanged
ConfidentialityNone
IntegrityLow
AvailabilityNone

Affected & Patched Versions

Affected Versions
  • sveltejs devalue < 5.6.4
Patched Versions
  • sveltejs devalue 5.6.4

What to do

Fix it during your normal patch cycle. No exploitation is confirmed yet.

  1. Check whether you run sveltejs devalue and which version.
  2. Update to a patched version listed above, then confirm the new version.

Timeline

  • Nov 8, 2026Published
  • Nov 13, 2026Record last modified

Score, severity and exploitation changes are tracked from the day Watchtower started logging them.

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External References

Data last checked: Nov 14, 2026 02:13 UTC