What is CVE-2026-34356?

CVE-2026-34356 is a high-severity vulnerability in Apache HTTP Server, classified under Heap-based Buffer Overflow. CVSS score: 7.5/10. Published 2026-06-08.

How severe is CVE-2026-34356?

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

Buffer overflow in Apache HTTP Server

CVE-2026-34356

Heap-based Buffer Overflow vulnerability in Apache HTTP Server with malicious backend servers and ProxyPassReverseCookie* This issue affects Apache HTTP Server: from 2.4.0 through 2.4.67. Users are recommended to upgrade to version 2.4.68, which fixes the issue.

Vulnerability class: Buffer Overflow

Published 2026-06-08 · last modified 2026-07-23.

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: 0.012 (68.3th percentile), scored 2026-10-25.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 68.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Apache HTTP Server
Apache Software Foundation HTTP Server — versions 2.4.0

Weakness classification (CWE)

CWE-122 — Heap-based Buffer Overflow

References

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

Frequently asked questions

What is CVE-2026-34356?: CVE-2026-34356 is a high-severity vulnerability in Apache HTTP Server, classified under Heap-based Buffer Overflow. CVSS score: 7.5/10. Published 2026-06-08.
How severe is CVE-2026-34356?: High severity. CVSS v3 base score is 7.5 out of 10.