CVE-2026-54891: Plaintext APPLICATION_DATA injected during TLS handshake delivered to client application post-handshake in ssl

CSIRTS triage

What

Plaintext APPLICATION_DATA is injected during the TLS handshake.

Who is affected

Applications using the affected TLS implementation are affected.

Urgency

Remediation is necessary as the severity is unknown but could impact security.

Action

Monitor for updates regarding this vulnerability.

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

Details

Source

Microsoft Security Response Center (INTL · vendor-psirt · site)

Severity

unknown

Published

2026-07-02

Exploitation

Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54891

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-2026-548910.14% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all scored CVEs.

Referenced CVEs

Same CVEs, other sources

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

• medium[NEW] [medium] Erlang/OTP: Multiple vulnerabilitiescert-bund
• lowCVE-2026-54891: Improper Enforcement of Message Integrity During Transmission in a Communication Channel vulne…nvd

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