CVE-2026-63566

HIGHNVD 7.57.5
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.4% (37th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Trending — 4 sources updated this week

Also known asEUVD-2026-91217 (ENISA EUVD) · GHSA-496x-2f25-59fj (GitHub Security Advisories)Source: ENISA EUVD

7.5EG
EchelonGraph verdictPlan mitigationThe upstream fix is not in a release yet: until the release ships, 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, then apply it (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: 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.

Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake message fragments, because the reassembly buffer for each incoming handshake message was allocated at the 24-bit length declared in the fragment header, without the check against the peer's maximum handshake message size that TLS already applied. A fragment carrying no payload can force an allocation of almost 16 MB, for each of up to 16 pending messages per handshake, before the handshake is authenticated. DTLS servers and DTLS clients are both affected; TLS is not.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
49
EG Risk 49/100

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)
Severity75% × 45%
Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
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 none (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: An upstream fix is merged but not yet in a tagged release. Until the release ships, 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, then apply it.
EPSS PROB
0.4%
EPSS %ILE
37th
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 (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.

EG Severity
7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS. 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).

An upstream fix is merged but not yet in a tagged release. Until the release ships, 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, then apply it.

Exploitation none (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 2, 2026

Last Modified

October 27, 2026

Advisory Details (2)

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

commit 99afef612458 (bcgit/bc-csharp)

Fix landed in bcgit/bc-csharp commit 99afef612458 — awaiting tagged release

https://github.com/bcgit/bc-csharp/commit/99afef612458f70f28e7824a09719bfc3a169bda
GitHub commit

commit 212d06474166 (bcgit/bc-csharp)

Fix landed in bcgit/bc-csharp commit 212d06474166 — awaiting tagged release

https://github.com/bcgit/bc-csharp/commit/212d06474166d5e85be72c2dd4898313aa5dd5f3

Vendor Advisories for CVE-2026-63566(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 10× in last 7d / 75× 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 it from the CNA feed. 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). Most recent first.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 4 repeat rows among the latest 89 are merged into the row they repeat.

  1. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  2. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  3. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  4. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  5. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.4% · 37th percentile
  6. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  7. 2026-10-27 16:30 UTCEG score recompute▼ 1.20
  8. 2026-10-27 16:29 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  9. 2026-10-27 16:26 UTCNVD updateCVSS v3 → 7.5
  10. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  11. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  12. 2026-10-25 14:13 UTCEG score recompute
  13. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  14. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  15. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  16. 2026-10-22 11:54 UTCEG score recompute
  17. 2026-10-22 11:54 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  18. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  19. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  20. 2026-10-20 09:16 UTCEG score recompute
  21. 2026-10-20 09:16 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  22. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  23. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  24. 2026-10-18 03:23 UTCEG score recompute
  25. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 29th percentile
Show 60 more
  1. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  2. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  3. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  4. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  5. 2026-10-13 11:58 UTCEG score recompute
  6. 2026-10-13 11:58 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  7. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  8. 2026-10-12 15:49 UTCEG score recompute
  9. 2026-10-12 01:14 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  10. 2026-10-11 19:33 UTCEG score recompute
  11. 2026-10-11 16:48 UTCEG score recompute
  12. 2026-10-11 14:10 UTCEG score recompute
  13. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  14. 2026-10-11 13:27 UTCEG score recompute
  15. 2026-10-11 13:27 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  16. 2026-10-11 01:51 UTCEG score recompute
  17. 2026-10-11 01:51 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  18. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  19. 2026-10-10 14:17 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  20. 2026-10-10 02:41 UTCEG score recompute
  21. 2026-10-10 02:41 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  22. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  23. 2026-10-09 15:08 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  24. 2026-10-09 03:04 UTCEG score recompute
  25. 2026-10-09 03:03 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  26. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  27. 2026-10-08 15:31 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  28. 2026-10-08 01:48 UTCEG score recompute
  29. 2026-10-08 01:48 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  30. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  31. 2026-10-07 14:15 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  32. 2026-10-07 02:30 UTCEG score recompute
  33. 2026-10-07 02:30 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  34. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  35. 2026-10-06 14:58 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  36. 2026-10-06 03:26 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  37. 2026-10-06 03:26 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  38. 2026-10-06 03:25 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  39. 2026-10-06 03:25 UTCEG score recompute
  40. 2026-10-06 03:25 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  41. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  42. 2026-10-05 15:50 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  43. 2026-10-05 04:00 UTCEG score recompute
  44. 2026-10-05 03:59 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  45. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  46. 2026-10-04 16:27 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  47. 2026-10-04 04:55 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  48. 2026-10-03 17:23 UTCEG score recompute
  49. 2026-10-03 17:23 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  50. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  51. 2026-10-03 05:52 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  52. 2026-10-02 18:20 UTCEG score recompute
  53. 2026-10-02 18:20 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  54. 2026-10-02 18:15 UTCEG score recompute
  55. 2026-10-02 18:15 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  56. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  57. 2026-10-02 14:45 UTCGHSA enrichmentGHSA-496x-2f25-59fj · GitHub severity HIGH
  58. 2026-10-02 07:25 UTCEG score recompute
  59. 2026-10-02 07:06 UTCEG score recomputeFirst assessed: 8.7 HIGH
  60. 2026-10-02 07:05 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-63566?
CVE-2026-63566 is a high-severity vulnerability; its CVE record was published on October 2, 2026. Memory allocation with excessive size value in the DTLS handshake reassembly (DtlsReliableHandshake, DtlsReassembler) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated DTLS peer to cause a denial of service through memory exhaustion via crafted handshake…
When was the CVE record for CVE-2026-63566 published?
The CVE record for CVE-2026-63566 was published on October 2, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 27, 2026; the record at its source may have been updated since.
Is CVE-2026-63566 actively exploited?
CVE-2026-63566 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (37th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63566?
CVE-2026-63566 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-63566?
An upstream fix for CVE-2026-63566 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-2026-63566 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2026-63566

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