Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes

Published Jun 12, 2026 · Updated Oct 23, 2026 · Also known as GHSA-x4gw-5cx5-pgmh

Severity · CVSSHIGH · 7.5

Known exploitationNot listed

EPSS / likelihood1.58%

QFinch risk score10 / 100

Original summary

Normalized public record · Updated Oct 23, 2026

Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes

Publisher and source text is retained separately from QFinch interpretation.

QFinch assessment

SslClientHelloHandler.decode() reads the 24-bit TLS handshake length and, when the ClientHello does not fit in the first record, eagerly allocates `ctx.alloc().buffer(handshakeLength)` (line 161). The guard at line 140 is `handshakeLength > maxClientHelloLength && maxClientHelloLength != 0`, and the commonly-used SniHandler/AbstractSniHandler constructors (SniHandler(Mapping), SniHandler(AsyncMapping), AbstractSniHandler()) pass maxClientHelloLength=0 and handshakeTimeoutMillis=0, so the length guard is disabled and no timeout is scheduled. A 16 MiB request exceeds the default pooled chunk size and becomes a huge/unpooled allocation performed immediately. The buffer is retained in the handler until the channel closes.

Evidence: public source records

Affected products

Affected scope reported by the available public evidence
Affected package, product or range	Fix status
Consult the referenced vendor advisory for affected versions.	Consult source advisory

Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.

Remediation

Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.

Confirm the affected product and reachable code path exist in your environment.
Apply the vendor-supported patch or mitigation from the primary advisory.
Rescan the exact deployed revision and retain verification evidence.

Review primary references

Evidence coverage

CVENVDOSVEPSSGHSA

SSVC priority: MEDIUM
Confidence: 10%
Aliases: GHSA-x4gw-5cx5-pgmh

Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.

Sources and record history

Record history

Published Jun 12, 2026 · Last refreshed Oct 23, 2026

Netty: SNI handler pre-allocates up to 16 MiB from nine attacker bytes

Original summary

QFinch assessment

Affected products

Remediation

Evidence coverage

Sources and record history

Record history

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