CVE-2026-63577

HIGHNVD 7.57.5
EchelonGraph scoreMEDIUM confidence

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

Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-10-02. NVD baseline CVSS 7.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3

Also known asEUVD-2026-91228 (ENISA EUVD) · GHSA-437r-hr8h-5f45 (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, then apply it (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.2%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.

Improper certificate validation in the directoryName name-constraint check (PkixNameConstraintValidator.WithinDNSubtree) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can have certificates issued by, a name-constrained intermediate CA to get certificates accepted by PKIX path validation whose subject distinguished name, or a directoryName subjectAltName, lies outside the CA's permitted subtrees, via a name that places other RDNs ahead of a copy of the permitted RDN sequence, because the check looks for the constraint's first RDN anywhere in the name and compares the remaining RDNs from that position, instead of requiring the constraint to be an initial prefix of the name as RFC 5280 sections 4.2.1.10 and 7.1 require.

CVSS v3
7.5
EG Score
7.5HIGHmedium confidence
EG Risk
34
EG Risk 34/100

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.
Exploitation0.2% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (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, then apply it.
EPSS PROB
0.2%
EPSS %ILE
11th
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.GitHub Security Advisory CVSS
EG Likelihood
0.2% 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 every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade 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. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.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 every mission impact level.

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, then apply it.

Exploitation none (CISA Vulnrichment) · Automatable no (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)60 days if the affected system is publicly exposed; Fix on system upgrade 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. In the directive's words, “Fix on system upgrade” means that, “unless conditions change”, the vulnerability “should be remediated the next time the vulnerable asset receives a scheduled major upgrade or rebuild”: its timelines are “dynamic as facts change”, and a KEV listing shortens them.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (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 28, 2026

Advisory Details (3)

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

commit 75c3c5766028 (bcgit/bc-csharp)

Fix landed in bcgit/bc-csharp commit 75c3c5766028 — awaiting tagged release

https://github.com/bcgit/bc-csharp/commit/75c3c576602886180ed92a63c89419e3bd63b392
GitHub commit

commit 606e9153b97a (bcgit/bc-csharp)

Fix landed in bcgit/bc-csharp commit 606e9153b97a — awaiting tagged release

https://github.com/bcgit/bc-csharp/commit/606e9153b97a265c70ca8293d21ec859344d7de8
Web page

CVE 2026 63577 · bcgit/bc-csharp Wiki · GitHub

https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63577

Vendor Advisories for CVE-2026-63577(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 8× in last 7d / 37× 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.

Showing the most recent 100 of 101 rows on record for this CVE.

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. None are among the latest 100 rows. The 1 oldest row on record is not shown and was not checked, so the counts can still include repeats.

  1. 2026-11-12 16:34 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  2. 2026-11-11 16:40 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  3. 2026-11-11 03:56 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH · GitHub CVSS 7.5
  4. 2026-11-10 18:55 UTCEchelonGraph re-scored
  5. 2026-11-10 18:55 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH · GitHub CVSS 7.5
  6. 2026-11-10 16:45 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  7. 2026-11-09 16:35 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  8. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  9. 2026-11-06 16:39 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  10. 2026-11-05 16:38 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  11. 2026-11-04 16:36 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  12. 2026-11-03 20:19 UTCEchelonGraph re-scored
  13. 2026-11-03 20:19 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH · GitHub CVSS 7.5
  14. 2026-11-03 16:48 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  15. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  16. 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  17. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  18. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  19. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 10th percentile
  20. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  21. 2026-10-28 14:48 UTCEchelonGraph re-scored▼ 0.70
  22. 2026-10-28 14:48 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  23. 2026-10-28 14:46 UTCNVD updateCVSS v3 → 7.5
  24. 2026-10-27 21:05 UTCEchelonGraph re-scored
  25. 2026-10-27 21:05 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
Show 75 more
  1. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  2. 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  3. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 14th percentile
  4. 2026-10-25 14:13 UTCEchelonGraph re-scored
  5. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  6. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  7. 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  8. 2026-10-22 11:57 UTCEchelonGraph re-scored
  9. 2026-10-22 11:57 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  10. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  11. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  12. 2026-10-20 10:32 UTCEchelonGraph re-scored
  13. 2026-10-20 10:31 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  14. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  15. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  16. 2026-10-18 03:23 UTCEchelonGraph re-scored
  17. 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  18. 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  19. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  20. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  21. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  22. 2026-10-13 11:58 UTCEchelonGraph re-scored
  23. 2026-10-13 11:58 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  24. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  25. 2026-10-12 15:49 UTCEchelonGraph re-scored
  26. 2026-10-11 23:47 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  27. 2026-10-11 19:33 UTCEchelonGraph re-scored
  28. 2026-10-11 16:48 UTCEchelonGraph re-scored
  29. 2026-10-11 14:10 UTCEchelonGraph re-scored
  30. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  31. 2026-10-11 12:33 UTCEchelonGraph re-scored
  32. 2026-10-11 12:32 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  33. 2026-10-11 01:22 UTCEchelonGraph re-scored
  34. 2026-10-11 01:21 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  35. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  36. 2026-10-10 13:58 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  37. 2026-10-10 02:48 UTCEchelonGraph re-scored
  38. 2026-10-10 02:48 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  39. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  40. 2026-10-09 15:38 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  41. 2026-10-09 04:27 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  42. 2026-10-08 17:17 UTCEchelonGraph re-scored
  43. 2026-10-08 17:17 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  44. 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  45. 2026-10-08 06:07 UTCEchelonGraph re-scored
  46. 2026-10-08 06:07 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  47. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  48. 2026-10-07 18:56 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  49. 2026-10-07 07:46 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  50. 2026-10-06 20:35 UTCEchelonGraph re-scored
  51. 2026-10-06 20:35 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  52. 2026-10-06 19:43 UTCEchelonGraph re-scored
  53. 2026-10-06 19:43 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  54. 2026-10-06 19:19 UTCEchelonGraph re-scored
  55. 2026-10-06 19:19 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  56. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  57. 2026-10-06 08:09 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  58. 2026-10-05 20:59 UTCEchelonGraph re-scored
  59. 2026-10-05 20:59 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  60. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  61. 2026-10-05 09:49 UTCEchelonGraph re-scored
  62. 2026-10-05 09:49 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  63. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  64. 2026-10-04 22:38 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  65. 2026-10-04 11:28 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  66. 2026-10-04 00:16 UTCEchelonGraph re-scored
  67. 2026-10-04 00:16 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  68. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  69. 2026-10-03 13:06 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  70. 2026-10-03 01:56 UTCEchelonGraph re-scored
  71. 2026-10-03 01:56 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  72. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  73. 2026-10-02 14:45 UTCGHSA enrichmentGHSA-437r-hr8h-5f45 · GitHub severity HIGH
  74. 2026-10-02 08:27 UTCEchelonGraph re-scored
  75. 2026-10-02 07:31 UTCEchelonGraph re-scoredFirst assessed: 8.2 HIGH

Frequently asked(5)

What is CVE-2026-63577?
CVE-2026-63577 is a high-severity vulnerability; its CVE record was published on October 2, 2026. Improper certificate validation in the directoryName name-constraint check (PkixNameConstraintValidator.WithinDNSubtree) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who controls, or can have certificates issued by, a name-constrained intermediate CA to get…
When was the CVE record for CVE-2026-63577 published?
The CVE record for CVE-2026-63577 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 28, 2026; the record at its source may have been updated since.
Is CVE-2026-63577 actively exploited?
CVE-2026-63577 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (11th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-63577?
CVE-2026-63577 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-63577?
An upstream fix for CVE-2026-63577 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-2026-63577 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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