What is CVE-2021-40511?

CVE-2021-40511 is a high-severity vulnerability in Obdasystems Mastro, classified under Improper Restriction of Recursive Entity References in DTDs (XML Entity Expansion). CVSS score: 7.5/10. Published 2022-06-21.

How severe is CVE-2021-40511?

High severity. CVSS v3 base score is 7.5 out of 10.

XXE in Obdasystems Mastro

CVE-2021-40511

OBDA systems’ Mastro 1.0 is vulnerable to XML Entity Expansion (aka “billion laughs”) attack allowing denial of service.

Published 2022-06-21 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.009 (58.9th percentile), scored 2026-10-04.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 58.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: +0.000

Affected products

Obdasystems Mastro — versions 1.0

Weakness classification (CWE)

CWE-776 — Improper Restriction of Recursive Entity References in DTDs (XML Entity Expansion)

References

www.obdasystems.com/mastro (Product, Vendor Advisory)
www.cyberiskvision.com/advisory/ (Third Party Advisory)

Frequently asked questions

What is CVE-2021-40511?: CVE-2021-40511 is a high-severity vulnerability in Obdasystems Mastro, classified under Improper Restriction of Recursive Entity References in DTDs (XML Entity Expansion). CVSS score: 7.5/10. Published 2022-06-21.
How severe is CVE-2021-40511?: High severity. CVSS v3 base score is 7.5 out of 10.