A flaw was found in Netty's SmtpResponseDecoder component. (CVE-2026-93563)
A vulnerability in Netty's SmtpResponseDecoder component allows a remote attacker, acting as a malicious or man-in-the-middle SMTP server, to send a crafted unbounded multi-line SMTP response without a terminator. This causes unbounded memory accumulation in the client's JVM heap, leading to an OutOfMemoryError and denial of service due to process crash.
AI Analysis
Technical Summary
CVE-2026-93563 is a medium severity vulnerability in Netty's SmtpResponseDecoder component. A remote attacker can exploit this by sending a specially crafted, unbounded multi-line SMTP response lacking a terminator, causing the client's Java Virtual Machine heap to accumulate memory without bounds. This results in an OutOfMemoryError and a denial of service condition due to process crash. The vulnerability affects multiple specific Netty versions as listed.
Potential Impact
The vulnerability causes a denial of service by crashing the client process through unbounded memory consumption in the JVM heap. There is no impact on confidentiality or integrity reported. No known exploits are currently in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Until a patch is available, consider limiting exposure to untrusted SMTP servers or intermediaries that could send malicious responses.
A flaw was found in Netty's SmtpResponseDecoder component. (CVE-2026-93563)
Description
A vulnerability in Netty's SmtpResponseDecoder component allows a remote attacker, acting as a malicious or man-in-the-middle SMTP server, to send a crafted unbounded multi-line SMTP response without a terminator. This causes unbounded memory accumulation in the client's JVM heap, leading to an OutOfMemoryError and denial of service due to process crash.
CVSS v3.1
Score 7.5high
Affected software
pkg:deb/ubuntu/netty?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/netty?arch=source&distro=esm-apps-legacy/xenialpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/bionicpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/focalpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/jammypkg:deb/ubuntu/netty?arch=source&distro=esm-apps/noblepkg:deb/ubuntu/netty?arch=source&distro=esm-apps/resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-93563 is a medium severity vulnerability in Netty's SmtpResponseDecoder component. A remote attacker can exploit this by sending a specially crafted, unbounded multi-line SMTP response lacking a terminator, causing the client's Java Virtual Machine heap to accumulate memory without bounds. This results in an OutOfMemoryError and a denial of service condition due to process crash. The vulnerability affects multiple specific Netty versions as listed.
Potential Impact
The vulnerability causes a denial of service by crashing the client process through unbounded memory consumption in the JVM heap. There is no impact on confidentiality or integrity reported. No known exploits are currently in the wild.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Until a patch is available, consider limiting exposure to untrusted SMTP servers or intermediaries that could send malicious responses.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-93563
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:Pro:22.04:LTS","Ubuntu:Pro:24.04:LTS","Ubuntu:Pro:26.04:LTS"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ab4be2ef7a7c54106eeec24
Added to database: 09/24/2026, 06:07:42 UTC
Last enriched: 09/24/2026, 06:29:25 UTC
Last updated: 09/25/2026, 02:47:33 UTC
Views: 3
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