EUVD-2026-82873
GHSA-mv3r-x43m-8mr7
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Network-reachable unauthenticated memory-exhaustion DoS with availability-only impact; AC:L retained per vendor though hostile-SMTP-peer requirement arguably supports AC:H.
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
Lifecycle Timeline
5DescriptionCVE.org
Unbounded multi-line response accumulation in SmtpResponseDecoder leads to memory-exhaustion DoS
Articles & Coverage 1
AnalysisAI
Memory exhaustion in Netty's SMTP client response decoder (SmtpResponseDecoder) allows an attacker who controls or can intercept the SMTP server that an application talks to, to force that application to accumulate unlimited multi-line responses until heap is exhausted. The defect is a pure availability issue (C:N/I:N/A:H, CVSS 7.5, AV:N/AC:L/PR:N/UI:N) and is reachable without authentication or user interaction on the victim side, but exploitation is conditional: the vulnerable JVM must have Netty's SMTP client codec active and must establish an SMTP session with a hostile or man-in-the-middle peer, since only server responses are parsed. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the affected application to use Netty's SMTP client codec (SmtpResponseDecoder) and to establish an SMTP session with a server the attacker controls or can intercept (MITM), since the vulnerable path parses multi-line server *responses*; the attacker then sends an unbounded stream of continuation lines to exhaust heap. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor CVSS of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) frames this as a network-reachable, unauthenticated, pure-availability denial of service, and the metrics are internally consistent with the description of unbounded multi-line SMTP response accumulation in Netty's SmtpResponseDecoder leading to memory exhaustion - I broadly agree with A:H and C:N/I:N. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | No vendor-released patch version is identified in the available data, so the first step is to obtain the current fixed Netty build and corresponding Red Hat errata through the advisory at https://access.redhat.com/security/cve/CVE-2026-93563 and the Bugzilla record https://bugzilla.redhat.com/show_bug.cgi?id=2536976, then upgrade the Netty dependency (and the Red Hat JBoss EAP 7, Fuse 7, RH-SSO 7 or Camel for Spring Boot 4 channel that carries it) to that release once the exact version is confirmed by the vendor. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all applications using the affected Red Hat products and determine if they use Netty's SMTP client codec for outbound email or SMTP communications; disable the SMTP client functionality if it is not business-critical, and restrict outbound SMTP traffic to known, trusted servers at the network perimeter. …
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