What is CVE-2021-33813?

CVE-2021-33813 is a high-severity vulnerability in Apache Solr, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 7.5/10. Published 2021-06-16.

How severe is CVE-2021-33813?

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

XXE in Apache Solr

CVE-2021-33813

An XXE issue in SAXBuilder in JDOM through 2.0.6 allows attackers to cause a denial of service via a crafted HTTP request.

Vulnerability class: XXE (XML External Entity)

Published 2021-06-16 · 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: 0.194 (97.3th percentile), scored 2026-10-19.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 97th percentile — 97.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.194 · newest: 0.194 · change: 0.000

Affected products

Apache Solr — versions 8.8.1, 8.9
Apache Tika — versions 1.25
Jdom
Oracle Communications Messaging Server — versions 8.1
Debian Linux — versions 9.0
Fedoraproject Fedora — versions 35

Weakness classification (CWE)

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

References

github.com/hunterhacker/jdom/pull/188 (Patch, Third Party Advisory)
github.com/hunterhacker/jdom/releases (Third Party Advisory, Release Notes)
lists.debian.org/debian-lts-announce/2021/06/msg00026.html (mailing-list, Mailing List, Third Party Advisory)
lists.apache.org/thread.html/r9974f64723875052e02787b2a5eda689ac5247c71b827d455… (mailing-list)
lists.apache.org/thread.html/rbc075a4ac85e7a8e47420b7383f16ffa0af3b792b84235847… (mailing-list)
lists.apache.org/thread.html/r89b3800cfabb1e773e49425e5d4239c28a659839a2eca6af3… (mailing-list)
lists.debian.org/debian-lts-announce/2021/07/msg00012.html (mailing-list, Mailing List, Third Party Advisory)
lists.apache.org/thread.html/rfb7a93e40ebeb1e0068cde0bf3834dcab46bb1ef06d6424db… (mailing-list)
lists.apache.org/thread.html/r845e987b7cd8efe610284958e997b84583f5a98d3394adc09… (mailing-list)
lists.apache.org/thread.html/r5674106135bb1a6ef57483f4c63a9c44bca85d0e2a8a05895… (mailing-list)

Frequently asked questions

What is CVE-2021-33813?: CVE-2021-33813 is a high-severity vulnerability in Apache Solr, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 7.5/10. Published 2021-06-16.
How severe is CVE-2021-33813?: High severity. CVSS v3 base score is 7.5 out of 10.