CVE-2026-42504: Quadratic complexity in WordDecoder.DecodeHeader in mime

highCVSS 7.5CVE-2026-42504

CSIRTS triage

Other

What: A quadratic complexity issue in WordDecoder.DecodeHeader in the mime component.
Who is affected: Systems utilizing the mime component with WordDecoder.
Urgency: Remediation is important due to the high severity rating of 7.5.
Action: Apply the necessary updates for the mime component.

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

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-2026-42504

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-2026-425040.56% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 43% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-42504	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] Golang Go: Multiple vulnerabilitiescert-bund

Recent advisories for Quadratic complexity in

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.

unknownCVE-2026-3276: Potential DoS via quadratic complexity in unicodedata.normalize()msrc · 2026-06-09