Paper/Archive/CVE-2026-59638

CVE-2026-59638

Legion of the Bouncy Castle Inc. BC-JAVA — JSSE hostname verifier CN-fallback enabled by default despite documented opt-in

EPSS 0.3%CVSS 9.3

critical.is priorityof 100

CVSS 9.3 (CNA)9.3 / 10 × 3027.9 Not in CISA KEV+300.0 EPSS percentile 28.1.281 × 205.6 No public exploit+100.0 SSVC exploitation: none+100.0

Description · from the CVE record

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).

Affected

ProductAffectedFixed inSource

BC-JAVA1.61 – < 1.851.85CNA

BC-LTS-JAVA2.73.0 – < 2.73.122.73.12CNA

BC-FJA1.0.7 – < 1.0.241.0.24CNA

BC-FJA2.0.0 – < 2.0.242.0.24CNA

BC-FJA2.1.0 – < 2.1.242.1.24CNA

Scores by source

bcorg (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber

CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

advisorygithub.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059638 patchgithub.com/bcgit/bc-java/commit/799bd15320a6310a447863638aa3df64acef829b patchgithub.com/bcgit/bc-java/commit/5ac55351cd1a8a7184d41c96a7ee87df0770240a