CVE-2026-21857

mediumpriority · track · 36EPSS 0.005 · 44 %ileexploit · PoCEUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

1 exploit · PoC

Likely / severe?

0.53% (44th) EPSS

CVSS 6.5 · medium

Is it mine?

3 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · nvd · osv

EPSS · scored 2026-10-23

REDAXO is a PHP-based content management system. Prior to version 5.20.2, authenticated users with backup permissions can read arbitrary files within the webroot via path traversal in the Backup addon's file export functionality. The Backup addon does not validate the `EXPDIR` POST parameter against the UI-generated allowlist of permitted directories. An attacker can supply relative paths containing `../` sequences (or even absolute paths inside the document root) to include any readable file in the generated `.tar.gz` archive. Version 5.20.2 fixes this issue.

cvss

Technical severity, 0–10. One row per scoring source.

8.3

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.5–8.3

v3.16.5mediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:Nprimary · NVD / NIST USexploitability 1.2 · impact 5.2

v4.08.3highCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:Nsecondary · ENISA EU

v4.08.3highCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Xsecondary · security-advisories@github.com

v4.07highCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Xsecondary · CVSS-BT (t0sche)

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: poc · Automatable: no · Technical Impact: partialcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-22USCWE-22USCWE-24USCWE-24US

exploits (1)

Public proof-of-concept and weaponised exploit code.

lukasz-rybak/CVE-2026-21857CVE-2026-21857 - Redaxo has Path Traversal in Backup Addon Leading to Arbitrary File ReadPoC · poc_in_github

affected products (3)

Products and version ranges known to be affected.

Redaxo REDAXO≤ < 5.20.2enisa_euvdEU
redaxo redaxo< 5.20.2nvdUScpe:2.3:a:redaxo:redaxo:*:*:*:*:*:*:*:*
Packagist redaxo/source< 5.20.2osvUSpkg:composer/redaxo/source

advisories (1)

Vendor and ecosystem advisories describing this.

GHSA-824x-88xg-cwrvRedaxo has Path Traversal in Backup Addon Leading to Arbitrary File Read2026-01-05ghsa · osvUS
### Summary Authenticated users with backup permissions can read arbitrary files within the webroot via path traversal in the Backup addon's file export functionality. <img width="664" height="899" alt="image" src="https://github.com/user-attachments/assets/fd1ca69e-b275-4daf-9a62-621cde6525f5" /> <img width="2358" height="445" alt="image" src="https://github.com/user-attachments/assets/fad81152-9e1b-413e-9823-09540a23e2fb" /> ### Details The Backup addon does not validate the `EXPDIR` POST parameter against the UI-generated allowlist of permitted directories. An attacker can supply relative paths containing `../` sequences (or even absolute paths inside the document root) to include any readable file in the generated `.tar.gz` archive. Vulnerable code: - `redaxo/src/addons/backup/pages/export.php` (lines 72-76) – directly uses `$_POST['EXPDIR']` - `redaxo/src/addons/backup/lib/backup.php` (lines ~413 & ~427) – concatenates unsanitized user input with base path This allows disclosure of sensitive files such as: - `redaxo/data/core/config.yml` → database credentials + password hashes of all backend users - `.env`, custom configuration files, logs, uploaded malicious files, etc. ### Affected versions ≤ 5.20.1 (confirmed working) ### Patched versions None (as of 2025-12-09) ### PoC – Extracting database credentials and password hashes 1. Log in as any user with Backup permission 2. Go to Backup → Export → Files <img width="1240" height="960" alt="image" src="https://github.com/user-attachments/assets/bc05ba18-9664-4be2-b637-4fec3a0f409a" /> 3. Intercept the request with Burp Suite <img width="2184" height="478" alt="image" src="https://github.com/user-attachments/assets/9fa754a1-2cd0-4d3d-a5cc-cfa34c8a1718" /> 4. Change one `EXPDIR[]` value to `../../../../var/www/html/redaxo/data/core` <img width="978" height="591" alt="image" src="https://github.com/user-attachments/assets/d15f5c7f-b72c-44cc-9be2-da8d3f26f124" /> 5. Send request → download archive <img width="423" height="131" alt="image" src="https://github.com/user-attachments/assets/db8a8bda-cdaf-4dea-812f-1e312da908e2" /> 6. Extract and open `data/core/config.yml` <img width="859" height="281" alt="image" src="https://github.com/user-attachments/assets/c8112ce1-5a1d-435f-953b-7eb4e711e042" /> Result: plaintext database password <img width="2534" height="1198" alt="image" src="https://github.com/user-attachments/assets/218ae917-868a-437e-98b0-6471b82c0b10" /> ### Impact Full compromise of the REDAXO installation: - Database takeover - Password hash extraction → offline cracking → admin access - When combined with other vulnerabilities → RCE CVSS 4.0 vector & score below. ### Credits Discovered by: Łukasz Rybak

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd osv NVD CVE.org MITRE

published 2026-01-07modified 2026-06-17

references (7)

External citations — patches, advisories, analysis.

scry

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