CVE-2021-26829
XSS in Scadabr ≤ 0.9.1
Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2021-26829 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Scadabr Scadabr. Its CVSS base score is 5.4 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Protocol or Service Impersonation (T1001.003); ranked in the top 1% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
OpenPLC ScadaBR is affected by a stored cross-site scripting vulnerability tracked as CVE-2021-26829. The flaw exists in versions through 0.9.1 on Linux and through 1.12.4 on Windows and is triggered via the system_settings.shtm component. It is classified under CWE-79 and carries a CVSS 3.1 base score of 5.4 reflecting network attack vector, low complexity, and required low-privileged authentication combined with user interaction.
An authenticated attacker can supply crafted input that is stored by the application and later rendered for other users. Successful exploitation allows the attacker to execute arbitrary script in the victim's browser session, resulting in limited impacts to confidentiality and integrity within a changed security context while availability remains unaffected.
The issue is listed in the CISA Known Exploited Vulnerabilities catalog, indicating confirmed real-world exploitation. Public references include forum threads on scadabr.com.br that report the security flaws along with demonstration material.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-13614
Vulnerability Data
OpenPLC ScadaBR through 0.9.1 on Linux and through 1.12.4 on Windows allows stored XSS via system_settings.shtm.
- CWE(s)
- KEV Date Added
- 28 November 2025
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.1.2V1.3.2
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.
Validates web inputs to reject script-related content that could produce XSS.
Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly target introduction of XSS via coding standards/testing (mostly), yet the single broad outcome leaves many specific neutralization vectors unaddressed (partial).
Patching and EOL replacement can remediate known XSS instances in libraries or frameworks (partial) but do nothing to enforce input neutralization in application code (none).
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
A.5.6 only promotes membership in groups to improve knowledge, receive alerts, and share information; it performs no action that stops XSS exploitation (or even the underlying neutralization defect) and is a pure dependency for other controls per the owner's labeling rule.