What is the CVSS score of CVE-2026-28509?

CVE-2026-28509 has a CVSS 3.1 base score of 6.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N. EPSS exploitation probability: 0.0%.

How to fix or mitigate CVE-2026-28509?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Langbot CVE-2026-28509

MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-03-06 security-advisories@github.com

XSS AI / ML Langbot

6.3

CVSS 3.1 · GitHub Advisory

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Vulnerability Assessment

Weakness	CWE CWE-79 OWASP Top 10:2025 A05:2025 - Injection ASVS 5.0 V1 - Encoding and Sanitization Output encoding, context-aware escaping MITRE ATT&CK 2 techniques across 2 tactics: Initial Access, Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS 6.3 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: Low. User interaction: Required.
Exploit ScenarioDerived	An attacker could exploit this vulnerability to a cross-site scripting (XSS) vulnerability.

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

No patch listed yet 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

LangBot is a global IM bot platform designed for LLMs. versions up to 4.8.7 is affected by cross-site scripting (xss) (CVSS 6.3).

RemediationAI

Fixed in version 4.8.7.. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability (CWE-79: Cross-site Scripting (XSS)) affects LangBot is a global IM bot platform designed for LLMs.. LangBot is a global IM bot platform designed for LLMs. Prior to version 4.8.7, LangBot’s web UI renders user-supplied raw HTML using rehypeRaw, which can lead to a cross-site scripting (XSS) vulnerability. This issue has been patched in version 4.8.7.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

GitHub Advisory PRIMARY 6.3 MEDIUM

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

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

Low

Availability

None

DescriptionGitHub Advisory

LangBot is a global IM bot platform designed for LLMs. Prior to version 4.8.7, LangBot’s web UI renders user-supplied raw HTML using rehypeRaw, which can lead to a cross-site scripting (XSS) vulnerability. This issue has been patched in version 4.8.7.

Executive ViewAI

Why It Matters

Organizations using LangBot should be aware of moderate risk from CVE-2026-28509, a cross-site scripting vulnerability rated CVSS 6.3. Attackers could inject scripts to steal sessions or perform actions as authenticated users. Organizations should apply vendor updates when available and monitor for exploitation.

Business Impact: Low

Compensating Controls

Apply vendor patch. If patching is delayed: implement CSP headers, enable HttpOnly cookies, deploy WAF XSS rules.

Threat Intelligence Overview

EPSS Score

0.0%

Top 91% exploitable

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

EPSS

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 No

EPSS 0.0%

Patch available No

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.