What is CVE-2026-33857?

CVE-2026-33857 is a medium-severity vulnerability in Apache HTTP Server, classified under Out-of-bounds Read. CVSS score: 5.3/10. Published 2026-05-04.

How severe is CVE-2026-33857?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Out-of-bounds Read in Apache HTTP Server

CVE-2026-33857

Out-of-bounds Read vulnerability in mod_proxy_ajp of Apache HTTP Server. This issue affects Apache HTTP Server: through 2.4.66. Users are recommended to upgrade to version 2.4.67, which fixes the issue.

Vulnerability class: Buffer Overflow

Published 2026-05-04 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.009 (59.4th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 59.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.009 · change: +0.005

Affected products

Apache HTTP Server
Apache Software Foundation HTTP Server — versions 0

Weakness classification (CWE)

CWE-125 — Out-of-bounds Read

References

httpd.apache.org/security/vulnerabilities_24.html (vendor-advisory, Vendor Advisory)
af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2026-33857?: CVE-2026-33857 is a medium-severity vulnerability in Apache HTTP Server, classified under Out-of-bounds Read. CVSS score: 5.3/10. Published 2026-05-04.
How severe is CVE-2026-33857?: Medium severity. CVSS v3 base score is 5.3 out of 10.