CVE-2026-44631: Apache HTTP Server: Heap Underflow in `ap_regname` via Signed Char Overflow

criticalCVSS 9.4CVE-2026-44631

CSIRTS triage

vendor: Apache product: Apache HTTP ServerOther

What: A heap underflow in `ap_regname` can occur via signed char overflow.
Who is affected: Deployments of Apache HTTP Server.
Urgency: Remediation is critical due to the critical severity rating and potential for exploitation.
Action: Immediately apply the latest security patch for 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: critical — CVSS 9.4
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44631

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-2026-446310.49% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 38% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-44631	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
unknownUSN-8516-1: Apache HTTP Server vulnerabilitiesubuntu · 2026-07-08
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