CVE-2026-75595
criticalpriority · track · 36EPSS 0.003 · 24 %ileDEFRNLUSEPSS · scored 2026-10-27
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–critical · 6.9–9.1
ssvc
A stakeholder decision — act, attend, or track — from exploitation and impact.
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (37)
Products and version ranges known to be affected.
advisories (6)
Vendor and ecosystem advisories describing this.
- NCSC-2026-0444Kwetsbaarheden verholpen in Oracle CommunicationsNL2026-10-21csaf · ncsc_nlNL
Oracle heeft 110 kwetsbaarheden verholpen in diverse Oracle Communications-producten, waaronder Oracle Communications Unified Assurance, Oracle Communications Cloud Native Core Security Edge Protection Proxy, Oracle Communications Service Catalog and Design en Oracle Communications Operations Monitor.
- WID-SEC-W-2026-3376Atlassian Bamboo, Bitbucket, Confluence, Fisheye/Crucible, Jira Software und Jira Service Management: Mehrere SchwachstellenDeutsch2026-09-15csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Atlassian Bamboo, Bitbucket, Confluence, Fisheye/Crucible, Jira Software und Jira Service Management ausnutzen, um beliebigen Programmcode auszuführen, Sicherheitsmaßnahmen zu umgehen, serverseitige Request-Forgery-Angriffe (SSRF) durchzuführen, Cross-Site-Scripting-Angriffe zu starten, sensible Informationen offenzulegen, Daten zu manipulieren oder Denial-of-Service-Zustände herbeizuführen.
- WID-SEC-W-2026-4056Atlassian Produkte (Bamboo, Bitbucket, Confluence, Crucible, Fisheye und Jira): Mehrere SchwachstellenDeutsch2026-10-20csaf · cert_bundDE
Ein Angreifer kann mehrere Schwachstellen in Atlassian Bamboo, Bitbucket, Confluence, Crucible, Fisheye und Jira ausnutzen, um Daten zu manipulieren, um seine Privilegien zu erhöhen, um einen Denial of Service Angriff durchzuführen, um Informationen offenzulegen, um einen Cross-Site Scripting Angriff durchzuführen, um Sicherheitsvorkehrungen zu umgehen und um beliebigen Programmcode auszuführen.
- WID-SEC-W-2026-4090Oracle Communications: Mehrere SchwachstellenDeutsch2026-10-20csaf · cert_bundDE
Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in Oracle Communications ausnutzen, um die Vertraulichkeit, Integrität und Verfügbarkeit zu gefährden.
- GHSA-c4c3-7fpv-j4q5Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext2026-09-08ghsa · osvUS
### Summary A fragmented TLS ClientHello whose handshake header spans multiple records makes Netty silently fall back to the default SslContext; where per-SNI selection is the sole mTLS gate, an unauthenticated attacker can bypass the route's mTLS requirement. ### Details In `io.netty.handler.ssl.SslClientHelloHandler#decode` the guard that should wait for the 4-byte handshake header checks the wrong offset - it ignores the 5-byte record header that precedes it - and therefore never fires: ```java if (handshakeLength == -1) { if (readerIndex + 4 > endOffset) { // Need more data to read HandshakeType and handshakeLength (4 bytes) return; } ``` When the first record's payload is < 4 bytes, `handshakeLength = in.getUnsignedMedium(readerIndex + SslUtils.SSL_RECORD_HEADER_LENGTH + 1);` leads to `IndexOutOfBoundsException `. That is caught by the generic `catch (Exception)` block, which calls `select(ctx, null)` - this is the default `SslContext`. Fallback to default on parse failure is a problem when per-SNI selection is the sole mTLS gate. ### Impact SNI routing bypass. Escalates to an unauthenticated mTLS bypass only when: - mTLS is enforced solely via per-SNI SslContext (clientAuth=REQUIRE) - the default/fallback SslContext is permissive (clientAuth=NONE/OPTIONAL) - no secondary peer-certificate verification exists at the application layer.
- CERTFR-2026-AVI-1385Multiples vulnérabilités dans les produits VMwareFrançais2026-10-26vendor · certfrFR
sources
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references (7) nvd
External citations — patches, advisories, analysis.
- https://github.com/netty/netty/commit/1b5abc6443b63726c72cdd285af2feb7ddbb8ff7Patch
- https://github.com/netty/netty/commit/9e0519239108a69b7e9bbc5e9182ee139a0d7961Patch
- https://github.com/netty/netty/pull/17213Issue TrackingPatch
- https://github.com/netty/netty/pull/17217Issue TrackingPatch
- https://github.com/netty/netty/releases/tag/netty-4.1.137.FinalRelease Notes
- https://github.com/netty/netty/releases/tag/netty-4.2.17.FinalRelease Notes
- https://github.com/netty/netty/security/advisories/GHSA-c4c3-7fpv-j4q5Vendor Advisory
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