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CVE-2026-75595 (GCVE-0-2026-75595)

Vulnerability from cvelistv5 – Published: 2026-08-19 21:00 – Updated: 2026-08-20 14:06
VLAI
Title
Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext
Summary
Netty is an asynchronous, event-driven network application framework. Prior to 4.1.137.Fina and 4.2.17.Final, io.netty.handler.ssl.SslClientHelloHandler#decode checks the wrong offset before reading the four-byte TLS handshake header, so a ClientHello whose handshake header spans records can cause an IndexOutOfBoundsException and invoke select(ctx, null). This selects the default SslContext instead of the SNI-specific context. In deployments where per-SNI clientAuth=REQUIRE is the sole mutual TLS gate, the default SslContext uses clientAuth=NONE or clientAuth=OPTIONAL, and no application-layer certificate verification exists, an unauthenticated remote attacker can bypass the protected route's mutual TLS requirement. This issue is fixed in versions 4.1.137.Final and 4.2.17.Final.
Severity
9.1 (Critical)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-20 14:05 UTC
CWE
  • CWE-754 - Improper Check for Unusual or Exceptional Conditions
Assigner
References
Impacted products
Vendor Product Version CPE status
netty netty Affected: < 4.1.137.Final
Affected: >= 4.2.0.Final, < 4.2.17.Final
guessed Create a notification for this product.
Show details on NVD website
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