What is the CVSS score of CVE-2026-86818?

CVE-2026-86818 has a CVSS 3.1 base score of 4.8 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N. EPSS exploitation probability: 0.2%.

Is there a public PoC exploit available for CVE-2026-86818?

Yes, a public proof-of-concept exploit is available for CVE-2026-86818. Prioritise patching immediately. EPSS: 0.2%.

Is there a patch available for CVE-2026-86818?

Yes, a patch is available for CVE-2026-86818. Update the affected software to the latest version immediately.

Node.js CVE-2026-86818

EUVD-2026-78403 MEDIUM

Encoding Error (CWE-172)

2026-09-15 openjs

GHSA-jvvf-x445-j334

Information Disclosure Node.js Red Hat Suse Fast Uri

4.8

CVSS 3.1 · Vendor: openjs

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Vulnerability Assessment

Weakness

CWE

CWE-172

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 15, 2026

The mailto scheme parser added to fast-uri 4.1.3 (and still present in 4.1.4) compares query field names against the reserved names 'to', 'subject' and 'body' while they are still percent-encoded, then decodes them only when storing them as generic headers — so a percent-encoded spelling of a reserved field is invisible to that check but is written back out as the literal field name during serialization. Any application built on Fastify, ajv or similar Node.js stacks that parses a mailto URI, validates, logs or displays the recipient list, and then re-serializes it with fast-uri before sending can be tricked into delivering mail to an attacker-chosen address, with subject and body content smuggled across the same roundtrip. The flaw is rated 4.8 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N, CWE-172 Encoding Error) and is fixed in fast-uri 4.1.5.

Affected VersionsENISA

fast-uri 4.1.3 <4.1.5

Affected Packages

npm fast-uri fix: 4.1.5

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in npm

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (openjs) PRIMARY 4.8 MEDIUM

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

SUSE 5.3 MEDIUM

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

Red Hat 4.8 MEDIUM

Primary rating from Vendor (openjs).

CVSS VectorVendor: openjs

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Patch available

Sep 15, 2026 - 12:16 EUVD

DescriptionCVE.org

fast-uri is a dependency-free RFC 3986 URI parser for Node.js, used by Fastify and ajv, that added a mailto scheme parser in version 4.1.3. In versions 4.1.3 and 4.1.4, the mailto parser compares each query field name to the reserved names to, subject, and body while the name is still percent-encoded, and decodes it only when storing it as a generic header, so a percent-encoded spelling of a reserved field name is not recognized as that field at parse time but is re-emitted as the literal field name when the parsed URI is serialized. An application that validates, logs, or displays the recipient list from the first parse and then serializes the URI and sends it can silently gain an attacker-chosen recipient, and the subject and body fields can be smuggled across the same roundtrip. The issue is fixed in fast-uri 4.1.5, and users should upgrade to 4.1.5 or later. As a workaround, do not act on a mailto URI that fast-uri has re-serialized without first decoding and re-validating its recipient, subject, and body fields.

Threat Intelligence Overview

EPSS Score

0.2%

Top 94% exploitable

Threat Intel

1 sources

Exploit

POC

Public exploit code exists

Data Quality

6 sources

Confidence: High

EUVD

NVD

CVE.org

EPSS

Vulnrichment GHSA Vendor

GitHub

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC Yes

EPSS 0.2%

Patch available Yes

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation

None

System Exposure· derived

Open

Automatable

Human Impact· derived

Medium

Technical Impact

Partial

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +24

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

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Vendor StatusVendor

SUSE

Severity: Moderate

Product	Status
SUSE Linux Enterprise Micro 5.3	Not-Affected
SUSE Linux Enterprise Micro 5.3	Not-Affected
SUSE Linux Enterprise Micro 5.3	Not-Affected
SUSE Linux Enterprise Micro 5.3	Not-Affected
SUSE Linux Enterprise Micro 5.4	Not-Affected

References

Advisories & patches

ADVISORY https://vuldb.com/vuln/404141 REF https://cna.openjsf.org/security-advisories.html REF https://github.com/fastify/fast-uri/security/advisories/GHSA-jvvf-x445-j334

Search Externally

GitHub PoC

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