CVE-2026-93563

Summary

A flaw was found in Netty's SmtpResponseDecoder component. A remote attacker, acting as a malicious or man-in-the-middle (MITM) SMTP server, could exploit this by sending a specially crafted, unbounded multi-line SMTP response without a terminator. This vulnerability leads to unbounded memory accumulation within the client's Java Virtual Machine (JVM) heap, causing an OutOfMemoryError and a denial of service (DoS) due to a process crash.

Affected Software

Weaknesses

• CWE-1035: CWE-1035

Workarounds

See https://github.com/netty/netty/security/advisories/GHSA-pq4x-537v-r54q for fixed versions and remediation guidance.

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: partial

References

• https://access.redhat.com/security/cve/CVE-2026-93563
• https://bugzilla.redhat.com/show_bug.cgi?id=2536976

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