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CVE-2026-31865

21
FAUCET Score

CVE-2026-31865 describes a prototype pollution vulnerability in the Elysia Typescript framework, affecting versions prior to 1.4.27. This flaw allows an attacker to override Elysia cookies by manipulating the prototype chain, such as using `__proto__`. Rated as MEDIUM severity (CVSS 5.3), it has a network attack vector with low complexity, requiring no privileges or user interaction, and primarily impacts data integrity. There is currently no evidence of active exploitation, nor are public exploit modules or significant community discussion available.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.4.27CPE matchmatch criteria
cpe:2.3:a:elysiajs:elysia:*:*:*:*:*:node.js:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
2.5
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.23%
Probability of exploitation in next 30 days
EPSS Percentile
14.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0023 is in the 5th percentile among its peer group of 23,725 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

npmpatch availablevia ghsa
Product: elysiaFixed in: 1.4.27

Vendor Advisories (1)

npmGHSA-8hq9-phh3-p2wpmedium

Elysia Cookie Value Prototype Pollution

Mar 17, 2026

References

github.com / elysiajs/elysia/commit/e9d6b1743fa7368ef942dce181f6a089757f6aab
Patch
github.com / elysiajs/elysia/security/advisories/GHSA-8hq9-phh3-p2wp
MitigationPatchVendor Advisory