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Vulnerability record · CVE-2026-59638 · published 3 August 2026

CVE-2026-59638: Bouncycastle bc-java vulnerability

Bouncycastle · Bc Java

In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback enabled by default despite documented opt-in. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).

9.3 CVSS 4.0 Critical EPSS 0.35% · top 74.5% CWE-297 · CWE-297
9.3CVSS 4.0 base score
0.35%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
3References
28 Aug 2026Last modified by NVD

Description

In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback enabled by default despite documented opt-in. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/bcgit/bc-java/commit/5ac55351cd1a8a7184d41c96a7ee87df0770240a Patch
https://github.com/bcgit/bc-java/commit/799bd15320a6310a447863638aa3df64acef829b Patch
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059638 Third Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-59638), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.