CVE-2026-116539

MEDIUMPre-NVD 5.95.9
EchelonGraph scoreHIGH confidence

“—” beside the score: it is equal to the CVSS score beside it.

Score 5.9 from GitHub Security Advisory (severity: HIGH) published 2026-10-26. A secondary CVSS source baseline 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
Elevated

Also known asEUVD-2026-109909 (ENISA EUVD) · GHSA-22qq-f4wc-4vfx (GitHub Security Advisories)Source: ENISA EUVD

5.9EG
EchelonGraph verdictPlan mitigationNo release containing the referenced fix is confirmed: check the referenced fix and the vendor's advisory for a release that contains it; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 5.9Exploit: No code on recordExposed services: Not assessed

A fix is referenced (a reference tagged "Patch", often a source commit), but no release containing it is confirmed — find the release that contains it; until it is applied, mitigate (WAF / firewall / segmentation).

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.

CVSS v3
5.9
EG Score
5.9MEDIUMhigh confidence
EG Risk
58
EG Risk 58/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity59% × 45%
Impact severity (EG Severity): CVSS 5.9 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule at low or medium mission impact and sooner than that at high.
EPSS PROB
0.4%
EPSS %ILE
34th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (5.9): severity, escalated by confirmed exploitation. This CVE's 5.9 is its impact severity (EG Severity), not escalated.

EG Severity
5.9 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-10). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).

A fix is referenced, but no release containing it is confirmed. Check the referenced fix and the vendor's advisory for a release that contains it; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation on your normal schedule at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; 60 days if it is not.

No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: it starts when an agency identifies the flaw on an asset and updates the CDM Agency and Federal Dashboard, and the directive counts patching, decommissioning the system or another action as remediation. Until a fixed release is applied, mitigate as this page's verdict says.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

October 26, 2026

Last Modified

November 2, 2026

Advisory Details (5)

Auto-updated Oct 26, 2026
Fix referenced — no release confirmed yet. Sources: github, github_commit.
Web page

Netty netty-tcnative before 2.0.84.Final Heap Buffer Overflow via OpenSSL BIO | Advisories | VulnCheck

https://www.vulncheck.com/advisories/netty-netty-tcnative-before-2.0.84-final-heap-buffer-overflow-via-openssl-bio
Web page

GitHub - netty/netty-tcnative: A fork of Apache Tomcat Native, based on finagle-native · GitHub

https://github.com/netty/netty-tcnative
Web page

netty-tcnative/openssl-dynamic/src/main/c/ssl.c at netty-tcnative-parent-2.0.83.Final · netty/netty-tcnative · GitHub

https://github.com/netty/netty-tcnative/blob/netty-tcnative-parent-2.0.83.Final/openssl-dynamic/src/main/c/ssl.c#L199
GitHub commit

commit 92dd66fd1243 (netty/netty-tcnative)

Fix landed in netty/netty-tcnative commit 92dd66fd1243 — awaiting tagged release

https://github.com/netty/netty-tcnative/commit/92dd66fd1243d85c05a61288f96367a70260b6b8
GitHub advisoryMentions a patch (unverified)

netty-tcnative NonApplicationBuffer RingBuffer Heap Overflow · Advisory · netty/netty-tcnative · GitHub

https://github.com/netty/netty-tcnative/security/advisories/GHSA-gf9q-9mg7-g5qh

Vendor Advisories for CVE-2026-116539(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
netty-tcnative2.0.28-1
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
netty-tcnative2.0.28-1
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
netty-tcnative2.0.28-1
  • every version on: no fix on record
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 25× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

  1. 2026-11-13 16:50 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  2. 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  3. 2026-11-11 16:38 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  4. 2026-11-11 06:53 UTCEchelonGraph re-scored
  5. 2026-11-11 06:53 UTCGHSA enrichmentGHSA-22qq-f4wc-4vfx · GitHub severity HIGH · GitHub CVSS 5.9
  6. 2026-11-10 16:42 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  7. 2026-11-09 16:34 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  8. 2026-11-08 16:38 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  9. 2026-11-07 16:38 UTCEPSS rescoreEPSS 0.4% · 34th percentile
  10. 2026-11-06 16:36 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  11. 2026-11-05 16:36 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  12. 2026-11-04 16:34 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  13. 2026-11-04 01:46 UTCEchelonGraph re-scored
  14. 2026-11-04 01:46 UTCGHSA enrichmentGHSA-22qq-f4wc-4vfx · GitHub severity HIGH · GitHub CVSS 5.9
  15. 2026-11-03 16:46 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  16. 2026-11-02 18:28 UTCEchelonGraph re-scored
  17. 2026-11-02 18:28 UTCGHSA enrichmentGHSA-22qq-f4wc-4vfx · GitHub severity HIGH · GitHub CVSS 5.9
  18. 2026-11-02 17:48 UTCEchelonGraph re-scored
  19. 2026-11-02 17:48 UTCGHSA enrichmentGHSA-22qq-f4wc-4vfx · GitHub severity HIGH · GitHub CVSS 5.9
  20. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  21. 2026-11-01 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  22. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  23. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  24. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  25. 2026-10-29 15:17 UTCEchelonGraph re-scored
Show 7 more
  1. 2026-10-29 15:17 UTCGHSA enrichmentGHSA-22qq-f4wc-4vfx · GitHub severity HIGH · GitHub CVSS 5.9
  2. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  3. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  4. 2026-10-26 16:30 UTCEchelonGraph re-scored
  5. 2026-10-26 16:01 UTCENISA EUVD ID recordedEUVD-2026-109909 · Source: ENISA EUVD
  6. 2026-10-26 15:31 UTCEchelonGraph re-scoredFirst assessed: 5.9 MEDIUM
  7. 2026-10-26 15:30 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-116539?
CVE-2026-116539 is a medium-severity vulnerability; its CVE record was published on October 26, 2026. 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,…
When was CVE-2026-116539 made public?
CVE-2026-116539 was made public on August 7, 2026: that is the date its CVE record's CNA, VulnCheck, gives for when the vulnerability was made public. The CVE record itself was published on October 26, 2026. EchelonGraph's copy of the record carries a last-modified date of November 2, 2026; the record at its source may have been updated since.
Is CVE-2026-116539 actively exploited?
CVE-2026-116539 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (34th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-116539?
CVE-2026-116539 has a CVSS base score of 5.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-116539?
A fix for CVE-2026-116539 is referenced (a reference tagged "Patch", often a source commit), but EchelonGraph has no release containing it on record. Check that reference and the vendor's advisory for a release that contains the fix and update to it; until then, restrict network exposure of the affected system or apply the vendor's mitigation. The vendor advisories EchelonGraph has for CVE-2026-116539 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-116539

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