# CVE-2026-116539: Netty netty-tcnative before 2.0.84.Final Heap Buffer Overflow via OpenSSL BIO

Status: published. Published: 2026-10-26. Updated: 2026-11-02.

Netty netty-tcnative before 2.0.84.Final contains a heap buffer overflow vulnerability in the tcn_write_to_bytebuffer BIO callback caused by failing to wrap the non-application ring buffer write index. Remote TLS peers can drive handshake, renegotiation, or post-handshake messages into this buffer, triggering an out-of-bounds memcpy that crashes the JVM process.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/netty/netty-tcnative/commit/92dd66fd1243d85c05a61288f96367a70260b6b8

## Affected products and versions

- netty / netty-tcnative (io.netty:netty-tcnative): ≥ 0; < 2.0.84.Final (affected, custom). Source: CNA: VulnCheck
- netty / netty-tcnative-boringssl-static (io.netty:netty-tcnative-boringssl-static): ≥ 0; < 2.0.84.Final (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.2 (high); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: 0.40% as of 2026-11-02; percentile 33.80%

- SSVC: exploitation poc; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-787

## Exploit evidence

- exploit: https://github.com/netty/netty-tcnative/security/advisories/GHSA-gf9q-9mg7-g5qh (ADP: CISA-ADP)

## References

- https://github.com/netty/netty-tcnative/security/advisories/GHSA-gf9q-9mg7-g5qh (CNA: VulnCheck; vendor-advisory)

- https://github.com/netty/netty-tcnative/commit/92dd66fd1243d85c05a61288f96367a70260b6b8 (CNA: VulnCheck; patch)

- https://github.com/netty/netty-tcnative/blob/netty-tcnative-parent-2.0.83.Final/openssl-dynamic/src/main/c/ssl.c#L199 (CNA: VulnCheck; technical-description)

- https://github.com/netty/netty-tcnative/releases/tag/netty-tcnative-parent-2.0.84.Final (CNA: VulnCheck; release-notes)

- https://github.com/netty/netty-tcnative (CNA: VulnCheck; product)

- https://www.vulncheck.com/advisories/netty-netty-tcnative-before-2.0.84-final-heap-buffer-overflow-via-openssl-bio (CNA: VulnCheck; third-party-advisory)

- https://github.com/netty/netty-tcnative/security/advisories/GHSA-gf9q-9mg7-g5qh (ADP: CISA-ADP; exploit)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-116539; retrieved 2026-11-02; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-116539; retrieved 2026-11-02; source updated Not reported

Revision: 223823bb6fd8738cb58c63a21cd5adac549ee1073d7f21f77b8c5d6b9d63897e

Canonical: https://y2.dev/cve/CVE-2026-116539

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