CVE-2026-59651 BKS keystore accepts legacy version with 16-bit integrity MAC key
Bouncy Castle for Java accepts legacy BKS keystores with weak 16-bit integrity MAC keys, allowing potential integrity bypasses.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-59651?
CVE-2026-59651 is a high-severity vulnerability in Bouncycastle Bc-Java, published on 3 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
In Bouncy Castle for Java before 1.85, BKS keystore accepts legacy version with 16-bit integrity MAC key. This issue also affects Bouncy Castle for Java LTS before 2.73.12.
Weakness: CWE-326
Which versions are affected by CVE-2026-59651?
It affects 2 products.
Products include Bouncycastle Bc-Java, Bouncycastle Bouncy Castle for Java Lts.
How do I fix CVE-2026-59651?
Upgrade to a fixed version.
Is CVE-2026-59651 being exploited?
There is no known exploitation of CVE-2026-59651 in the wild and no public exploit code.
Other vulnerabilities in Bouncycastle Bc-Java
- CVE-2007-6721 Legion of the Bouncy Castle Java Cryptography API Bleichenbacher Oracle Vulnerability
- CVE-2018-1000613 Deserialization of Untrusted Data in Bouncy castle
- CVE-2026-58062 Stapled OCSP response accepted without binding to the checked certificate
- CVE-2026-59638 JSSE hostname verifier CN-fallback enabled by default despite documented opt-in
- CVE-2026-59650 MTI/A0 DH agreement exponentiates unvalidated peer value
Sources
Also known as CLEANSTART-2026-BJ11683, CLEANSTART-2026-FQ48226, CLEANSTART-2026-JU77180, CLEANSTART-2026-XM48481, CLEANSTART-2026-XP43245, DEBIAN-CVE-2026-59651 and 2 more.