What’s Vulnerable › Vulnerabilities

CVE-2026-93563: Io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-18 · updated 2026-09-25
• Weakness: CWE-1035

Description

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 products

• Red Hat build of Apache Camel for Spring Boot 4: all versions
• Red Hat JBoss Enterprise Application Platform 7: all versions
• Red Hat Single Sign-On 7: all versions

References

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

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