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Cervantes CVE-2026-115993

| EUVDEUVD-2026-109259 MEDIUM
Cross-site Scripting (XSS) (CWE-79)
2026-10-24 Grayback GHSA-fgjg-4v79-vhpp
6.8
CVSS 3.1 · Vendor: Grayback
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain low-privileged Cervantes account
  2. Delivery
    Store script payload in Checklist Notes field
  3. Exploit
    Privileged user views the checklist
  4. Execution
    Payload executes in victim browser
  5. Impact
    Hijack elevated session / act as admin

Vulnerability Assessment

Weakness
CWE
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.

Exploitation Conditions

Exploitation requires an authenticated account on the Cervantes instance with permission to write to the 'Notes' field of a Checklist (PR:L), and a second, higher-privileged user must subsequently view that checklist for the stored payload to fire (UI:R). The impact is realized only because the victim holds elevated privileges, so the attack's value depends on a multi-user deployment where low- and high-privilege users share checklists. Limiting factors: it is not exploitable by a fully unauthenticated outsider, it needs victim interaction (viewing the affected note), and a single-user or isolated instance offers no privilege-escalation target.

Impact

This is a moderate, authenticated-user XSS issue rather than a drop-everything emergency. The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N, base 6.8) tells a consistent story: network-reachable, low attack complexity, but it REQUIRES an existing low-privileged authenticated account (PR:L) to inject the payload AND a victim to view the malicious Notes field (UI:R). The scope change (S:C) plus C:H reflects the real danger - a stored payload executing in a higher-privileged user's (e.g. admin/project-owner) browser session, enabling session or privilege theft 'with elevated privileges' as the description states. No EPSS score, KEV listing, or verified proof-of-concept was provided, so there is no evidence of active or at-scale exploitation; the vuln.today decision label is 'this_month,' not act_now or emergency, which aligns with a patch-on-normal-cadence posture. The 'RCE' tag in the input is misleading: the description describes arbitrary code execution in another user's BROWSER (client-side script), not server-side remote code execution - treat this as stored XSS, not RCE. Overall a real but bounded risk requiring an insider or a compromised low-priv account plus victim interaction.

Exploit ScenarioDerived

A low-privileged user (or attacker controlling such an account) on a shared Cervantes pentest-collaboration instance stores a malicious script in the 'Notes' field of a Checklist. When a higher-privileged teammate (e.g. an administrator or project owner) later opens that checklist, the script executes in their browser session with their elevated privileges, allowing session hijacking or actions on their behalf. No verified public exploit code was identified in the provided data, though the injection is straightforward given AC:L.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.4% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 24, 2026

Stored cross-site scripting in the 'Notes' field of Checklists in Cervantes v1.3-beta lets an authenticated user with permission to write notes plant a payload that executes in another user's browser when that checklist is viewed. Because the victim is expected to hold higher privileges than the author, the injected script can act with elevated rights - the assessed vector is CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N (6.8 base), reflecting a scope change and high confidentiality impact, and the tags attached to this record cite both XSS and RCE outcomes. Exploitation requires a multi-user deployment where low- and high-privilege users share checklists, plus victim interaction; no public exploit code was identified at time of analysis, and the vulnerability is not listed as actively exploited.

RemediationAI

A vendor patch is available per the advisory pages at https://www.grayback.es/advisories and https://www.grayback.es/en/advisories; review those advisories to confirm the exact fixed release for the v1.3-beta line and upgrade to it, since no specific patched version number is given in the supplied data. Where upgrading cannot be done immediately, the practical compensating controls follow from the exploitation prerequisites rather than from anything the sources prescribe: treat every account that can write to a Checklist's Notes field as a potential injection source and restrict that permission to trusted users, and avoid sharing checklists across privilege boundaries - do not let low-privilege accounts add notes to checklists that administrators review. Both measures reduce exposure but do not remove the underlying rendering flaw, so they are interim only. There is no mitigation in the available evidence that the vendor has stated as equivalent to updating.

Affected VersionsENISA

cervantes alpha 0.3 ≤1.3-beta

Affected Packages

euvd cervantes_alpha no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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

Technical ContextAI · show details

The flaw is a CWE-79 cross-site scripting issue of the stored (persistent) variety in a web application, identified by the CPE cpe:2.3:a:cervantessec:cervantes:*:*:*:*:*:*:*:* and reported against Cervantes v1.3-beta. User-supplied content entered into the Notes field of a Checklist is retained server-side and later rendered to other users without adequate neutralization, so script supplied by the author is executed in the viewer's browser session rather than the author's. The CVSS scope-change component (S:C) captures the consequence that the script runs in the context of the higher-privileged viewer, so the confidentiality impact applies to that victim's data rather than to the attacker's own account; the integrity impact is assessed as low and availability as none. The specific encoding or sanitization gap in the Notes rendering path, and the exact trigger mechanics, are not described in the available sources; the record's tags (XSS, RCE) indicate the reporters consider script execution in the privileged browser a viable path toward broader code execution, but that chain is not detailed in the supplied evidence.

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Severity by source

Vendor (Grayback) PRIMARY 6.8 MEDIUM
AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:N
vuln.today AI 7.6 HIGH

Stored XSS needs a low-priv authenticated account (PR:L) and a victim view (UI:R); script runs in the victim's higher-priv browser context (S:C, C:H) and can perform limited actions (I:L).

3.1 AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:L/VA:N/SC:L/SI:L/SA:N

Primary rating from Vendor (Grayback).

CVSS VectorVendor: Grayback

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

DescriptionCVE.org

Stored XSS vulnerability in the “Notes” field of the Checklists in Cervantes version v1.3-beta could allow an attacker to execute arbitrary code in another user's browser with elevated privileges

Threat Intelligence Overview

EPSS Score
0.4%
Top 65% exploitable
Prevalence
Low
niche open-source pentest collaboration platform, small specialist user base
Social Media
1
Sightings
Data Quality
5 sources
Confidence: Medium

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 0.4%
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· derived
None
System Exposure· derived
Open
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

34
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +34
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

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