CVE-2026-70454: rsync < 3.5.0 TLS Certificate Validation Bypass via SSL/OpenSSL Mode

CSIRTS triage

What

TLS certificate validation is bypassed in SSL/OpenSSL mode, allowing man-in-the-middle attacks.

Who is affected

rsync deployments prior to 3.5.0 using SSL/TLS for encrypted transfers over untrusted networks.

Urgency

High severity; enables interception of encrypted transfers if certificate validation is not enforced.

Action

Upgrade rsync to version 3.5.0 or later and verify TLS certificate validation is enabled.

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 8

Published

2026-08-11

Exploitation

Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70454

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-2026-704540.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all EPSS-scored CVEs.

Referenced CVEs

Same CVEs, other sources

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

• high[NEW] [high] Rsync: Multiple vulnerabilitiescert-bund
• highCVE-2026-70454: rsync 3.2.0 through 3.2.3 (openssl mode) and rsync-ssl through 3.4.4 (stunnel mode) contain a …nvd

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