CVE-2026-34563: CI4MS: Backup Management Full Account Takeover for All-Roles & Privilege-Escalation via Stored DOM Blind XSS

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.4%, percentile 32: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 32% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes ci4-cms-erp/ci4ms (Composer (PHP)) <= 0.28.6.0, fixed in 0.31.0.0. Check your lockfile, including transitive dependencies.

What it is

CI4MS is a CodeIgniter 4-based CMS skeleton that delivers a production-ready, modular architecture with RBAC authorization and theme support. Prior to version 0.31.0.0, the application fails to properly sanitize user-controlled input when handling backup uploads and processing backup metadata. An attacker can inject a malicious JavaScript payload into the backup filename via the uploaded xss.sql, which uses SQL functionality to insert the XSS payload server-side. This stored payload is later rendered unsafely in multiple backup management views without proper output encoding, leading to stored blind cross-site scripting (Blind XSS). This issue has been patched in version 0.31.0.0.

From the GitHub advisory

Summary Vulnerability: Stored DOM Blind XSS via Backup Management Filename (Persistent Payload Injection) - Stored Cross-Site Scripting (Blind XSS) via Unsanitized Backup Filename in Backup Management

Description The application fails to properly sanitize user-controlled input when handling backup uploads and processing backup metadata. An attacker can inject a malicious JavaScript payload into the backup filename via the uploaded xss.sql, which uses SQL functionality to insert the XSS payload server-side.

This stored payload is later rendered unsafely in multiple backup management views without proper output encoding, leading to stored blind cross-site scripting (Blind XSS).

Affected Functionality - Backup upload functionality - Backup processing functionality - Backup storage and retrieval logic

Attack Scenario - An attacker uploads xss.sql which uses SQL functionality to insert a malicious XSS payload into the backup filename field server-side. - The application stores this filename without sanitization or encoding. - The payload persists and executes whenever the backup filename is rendered in affected views. - The attacker does not see immediate execution, making this a Blind XSS scenario that triggers only when an administrator or privileged user views the backup management panel.

Weakness type: CWE-79.

Product: ci4-cms-erp/ci4ms (Composer (PHP)) · Assigned by: GitHub_M · Published: 2026-04-01

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.39% probability of exploitation activity in the next 30 days; percentile 32.

Timeline

• 2026-04-01 — CVE record published by GitHub_M
• 2026-04-01 — GitHub-reviewed advisory GHSA-85m8-g393-jcxf published (critical)
• 2026-04-02 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-85m8-g393-jcxf github.com
2. CVE.org record CVE-2026-34563 cve.org
3. NVD entry CVE-2026-34563 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

Critical Composer (PHP) advisories · Today’s Security Digest