CVE-2026-6678: Integer underflow in wc_PKCS7_DecryptOri handling crafted Other Recipient Info

mediumCVSS 5.3CVE-2026-6678

CSIRTS triage

Other

What: Integer underflow in wc_PKCS7_DecryptOri handling crafted Other Recipient Info.
Who is affected: Deployments using the affected cryptographic functions.
Urgency: Remediation is medium urgency due to the medium severity rating.
Action: Apply the relevant patches to fix the integer underflow issue.

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

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 5.3
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-6678

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-2026-66780.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-6678	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

mediumCVE-2026-6678: Integer underflow in wc_PKCS7_DecryptOri when handling crafted Other Recipient Info, leading to…nvd

Recent advisories for Integer underflow 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.

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