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Io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos

Red Hat · CVE-2026-93563
0 news outlets0 CERTs and agencies0 researchers

Assessment: Track

SSVC decision points: exploitation none, automatable yes, technical impact partial, deployment low.

What is it?

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.

Evidence

No coverage recorded yet.

Exploitation

  • Public proof of concept
  • Exploited in the wild
  • Listed as known exploited
CVSS
7.5
EPSS
0.3%
First seen
2 d ago
Status
corroborated

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