CVE-2026-34355: Apache HTTP Server: mod_proxy_html buffer overflow

highCVSS 7.5CVE-2026-34355

CSIRTS triage

vendor: Apache product: Apache HTTP ServerOther

What: A buffer overflow exists in mod_proxy_html.
Who is affected: Deployments of Apache HTTP Server using mod_proxy_html.
Urgency: Remediation is urgent due to the high severity rating and potential for exploitation.
Action: Update to the latest version of Apache HTTP Server.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.5
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-34355

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-343550.80% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 52% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-34355	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

high[UPDATE] [high] Apache HTTP Server: Multiple vulnerabilitiescert-bund
unknownUSN-8516-1: Apache HTTP Server vulnerabilitiesubuntu

Recent advisories for Apache HTTP Server

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

high[UPDATE] [high] Apache HTTP Server: Multiple vulnerabilitiescert-bund · 2026-07-09
high[UPDATE] [high] Apache HTTP Server: Multiple vulnerabilitiescert-bund · 2026-07-09
high[UPDATE] [high] Apache HTTP Server: Multiple vulnerabilitiescert-bund · 2026-07-09
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