What is CVE-2020-11991?

CVE-2020-11991 is a high-severity vulnerability in Apache Cocoon, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 7.5/10. Published 2020-09-11.

How severe is CVE-2020-11991?

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

Is CVE-2020-11991 known to be exploited?

24 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

XXE in Apache Cocoon

CVE-2020-11991

When using the StreamGenerator, the code parse a user-provided XML. A specially crafted XML, including external system entities, could be used to access any file on the server system.

Vulnerability class: XXE (XML External Entity)

Published 2020-09-11 · 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:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.725 (99.4th percentile), scored 2026-10-17.

High probability of exploitation in the next 30 days — patch promptly. 99th percentile — 99.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.725 · newest: 0.725 · change: 0.000

Affected products

Apache Cocoon
Apache Cocoon — versions Apache Cocoon 2.1.0 to 2.1.12

Weakness classification (CWE)

CWE-611 — Improper Restriction of XML External Entity Reference (XXE)

Public proof-of-concept exploits

References

lists.apache.org/thread.html/r77add973ea521185e1a90aca00ba9dae7caa8d8b944d92421… (Exploit, Mailing List, Vendor Advisory)

Frequently asked questions

What is CVE-2020-11991?: CVE-2020-11991 is a high-severity vulnerability in Apache Cocoon, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 7.5/10. Published 2020-09-11.
How severe is CVE-2020-11991?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2020-11991 known to be exploited?: 24 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.