CVE-2026-59638: bouncycastle bc-java
CVSS: 9.3v4.0CriticalAnalyzed
AliasesUBUNTU-CVE-2026-59638DEBIAN-CVE-2026-59638
Published 03-08-2026Last modified 03-08-2026
Vulnerability summary
CVE-2026-59638 is a critical (CVSS 9.3) vulnerability in bouncycastle bc-java. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 26.6% of scored vulnerabilities.
CVSS score
9.3/10
010
Critical · v4.0 (CVE.org)EPSS score
0.34%
0%100%
Low · +0.14 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 5 · Related 5Timeline
- 03-08-2026PublishedVulnerability first disclosed.
- 03-08-2026Last modifiedVulnerability information updated.
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 metrics
6 scores · 4 sources · 2 versionsCritical 9.3Preferred score · CVE.org (CNA)
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/U:AmberSourcesAll 3 agree
- OSV · UbuntuEcosystem advisory · calculated9.3CriticalCVSS: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
- NVDNIST9.3CriticalCVSS: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:X/V:X/RE:X/U:Amber
Medium 6.5Preferred score · OSV · Ubuntu (Ecosystem advisory) · calculated from vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:NSourcesAll 3 agree
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS trend
Probability
0.34%
Chance of exploitation in the next 30 days
Percentile
27%
Versus all other CVEs
30-day change
+0.14 pp
From 0.21% on 19-09-2026
19-09-202619-10-2026
EPSS score0.34%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Bouncycastle3 products
- bc-java< 1.85
- bctls-fips≥ 1.0.0, < 1.0.24 | ≥ 2.0.19, < 2.0.24 | ≥ 2.1.20, < 2.1.24
- bouncy_castle_for_java_lts≤ 2.73.11
Legion of the bouncy castle inc.3 products
- bc-fja≥ 1.0.7, < 1.0.24 | ≥ 2.0.0, < 2.0.24 | ≥ 2.1.0, < 2.1.24
- bc-java≥ 1.61, < 1.85
- bc-lts-java≥ 2.73.0, < 2.73.12
Debian1 product
- bouncycastleAll versions (No fix recorded) | < 1.86-1
Ubuntu1 product
- bouncycastleAll versions (No fix recorded)
4 vendors · 8 products
References
6 links- github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059638Vendor AdvisoryREPORTThird Party Advisory
