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.
CVE-2026-63577
This high-severity CVE scores 8.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2% (13th 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).
- High severity, but no confirmed exploitation yet
An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.
- CVSS v3
- 8.2
- EG Score
- 8.2HIGHmedium confidence
- EG Risk
- 41EG Risk 41/100CISA 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 computedSeverity82% × 45%Exploitation0% × 40%Automatability30% × 15%CISA SSVC: Track at low or medium mission impact; Track or 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
- 0.2%
- EPSS %ILE
- 13th
- KEV
- Not listed
CISA SSVCTrack at low or medium mission impact; Track or 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 (no KEV listing, exploit record or EPSS ≥ 50%) · Automatable unknown (not published for this CVE) · Technical impact partial (CVSS below 9.0). 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 (3)
Auto-updated Oct 2, 2026commit 75c3c5766028 (bcgit/bc-csharp)
Fix landed in bcgit/bc-csharp commit 75c3c5766028 — awaiting tagged release
https://github.com/bcgit/bc-csharp/commit/75c3c576602886180ed92a63c89419e3bd63b392commit 606e9153b97a (bcgit/bc-csharp)
Fix landed in bcgit/bc-csharp commit 606e9153b97a — awaiting tagged release
https://github.com/bcgit/bc-csharp/commit/606e9153b97a265c70ca8293d21ec859344d7de8CVE 2026 63577 · bcgit/bc-csharp Wiki · GitHub
https://github.com/bcgit/bc-csharp/wiki/CVE-2026-63577Vendor 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 11× in last 7d / 11× 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.
- 2026-10-04 00:16 UTCEG score recompute
- 2026-10-04 00:16 UTCGHSA enrichment
- 2026-10-03 14:26 UTCEPSS rescore
- 2026-10-03 13:06 UTCGHSA enrichment
- 2026-10-03 01:56 UTCEG score recompute
- 2026-10-03 01:56 UTCGHSA enrichment
- 2026-10-02 17:56 UTCEPSS rescore
- 2026-10-02 14:45 UTCGHSA enrichment
- 2026-10-02 08:27 UTCEG score recompute
- 2026-10-02 07:31 UTCEG score recompute
- 2026-10-02 07:30 UTCMITRE cvelistV5first tracked
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Frequently asked(5)
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Dependency Blast Radius
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