CVE-2026-63569

CRITICALPre-NVD 9.19.1—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (31st percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 4 sources updated this week
9.1EG
EchelonGraph verdictPlan mitigationSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 9.1Exploit: None knownExposed services: Not assessed

An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.

Improper input validation in DHAgreement.CalculateAgreement (MTI/A0 two-pass Diffie-Hellman) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an on-path attacker to make the local party compute an agreed value the attacker already knows, defeating the key authentication MTI/A0 is meant to provide. It also allows a malicious peer to learn the local static private key modulo the small factors of p-1, and to recover it entirely in groups with many such factors. The attack uses a crafted out-of-range or small-order ephemeral value, and works because that value is raised to the static private key without the range and subgroup-membership checks applied to DH public keys. Only applications that call DHAgreement directly are affected.

CVSS v3
9.1
EG Score
9.1CRITICALmedium confidence
EG Risk
56
EG Risk 56/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity91% × 45%
Exploitation0% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release.
EPSS PROB
0.4%
EPSS %ILE
31st
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high until it ships, then apply the release.

Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

October 2, 2026

Last Modified

October 2, 2026

Advisory Details (2)

Auto-updated Oct 2, 2026
Upstream fix merged — awaiting tagged release. Sources: github_commit.
github_commit

commit fe236ad207c5 (bcgit/bc-csharp)

Fix landed in bcgit/bc-csharp commit fe236ad207c5 — awaiting tagged release

https://github.com/bcgit/bc-csharp/commit/fe236ad207c5960eeae1ebb6560c783a3bb5b692
generic

CVE 2026 63569 · bcgit/bc-csharp Wiki · GitHub

https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63569

Vendor Advisories for CVE-2026-63569(1)

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

Weakness Classification(1)

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

Data Freshness Timeline

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

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-05 07:40 UTCGHSA enrichment
  2. 2026-10-05 03:22 UTCEG score recompute
  3. 2026-10-05 03:22 UTCGHSA enrichment
  4. 2026-10-04 23:22 UTCEPSS rescore
  5. 2026-10-04 23:03 UTCGHSA enrichment
  6. 2026-10-04 18:43 UTCGHSA enrichment
  7. 2026-10-04 14:24 UTCGHSA enrichment
  8. 2026-10-04 10:07 UTCGHSA enrichment
  9. 2026-10-04 05:49 UTCGHSA enrichment
  10. 2026-10-04 01:31 UTCGHSA enrichment
  11. 2026-10-03 21:12 UTCGHSA enrichment
  12. 2026-10-03 16:54 UTCEG score recompute
  13. 2026-10-03 16:54 UTCGHSA enrichment
  14. 2026-10-03 14:26 UTCEPSS rescore
  15. 2026-10-03 12:37 UTCGHSA enrichment
  16. 2026-10-03 08:19 UTCGHSA enrichment
  17. 2026-10-03 03:58 UTCGHSA enrichment
  18. 2026-10-02 23:38 UTCGHSA enrichment
  19. 2026-10-02 19:20 UTCEG score recompute
  20. 2026-10-02 19:20 UTCGHSA enrichment
  21. 2026-10-02 19:10 UTCEG score recompute
  22. 2026-10-02 19:10 UTCGHSA enrichment
  23. 2026-10-02 19:03 UTCEG score recompute
  24. 2026-10-02 19:03 UTCGHSA enrichment
  25. 2026-10-02 17:56 UTCEPSS rescore
Show 5 more
  1. 2026-10-02 14:45 UTCGHSA enrichment
  2. 2026-10-02 11:44 UTCGHSA enrichment
  3. 2026-10-02 07:25 UTCEG score recompute
  4. 2026-10-02 07:06 UTCEG score recompute
  5. 2026-10-02 07:05 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-63569?
CVE-2026-63569 is a critical vulnerability published on October 2, 2026. Improper input validation in DHAgreement.CalculateAgreement (MTI/A0 two-pass Diffie-Hellman) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an on-path attacker to make the local party compute an agreed value the attacker already knows, defeating the key authentication MTI/A0 is…
When was CVE-2026-63569 disclosed?
CVE-2026-63569 was first published on October 2, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-63569 actively exploited?
CVE-2026-63569 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (31st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63569?
CVE-2026-63569 has a CVSS base score of 9.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-63569?
An upstream fix for CVE-2026-63569 has been merged but is not yet in a tagged release. Until it ships, restrict network exposure of the affected system or apply the vendor's mitigation, then update to the release that contains the fix. The vendor advisories EchelonGraph has for CVE-2026-63569 are linked in the Vendor Advisories panel on this page.

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