CVE-2026-12816 IESEngine stream-mode MAC forgery via length-dependent KDF split
Attackers can forge MACs in stream mode due to a length-dependent KDF split flaw in the Bouncy Castle Java library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-12816?
CVE-2026-12816 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, with no action from the victim.
Official description
In Bouncy Castle for Java before 1.85, IESEngine stream-mode MAC forgery via length-dependent KDF split. This issue also affects Bouncy Castle for Java LTS before 2.73.12.
Weakness: CWE-354
Which versions are affected by CVE-2026-12816?
It affects 2 products.
Products include Bouncycastle Bc-Java, Bouncycastle Bouncy Castle for Java Lts.
How do I fix CVE-2026-12816?
Upgrade to a fixed version.
Is CVE-2026-12816 being exploited?
There is no known exploitation of CVE-2026-12816 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-JP50246, CLEANSTART-2026-JX92786, CLEANSTART-2026-KC23930, CLEANSTART-2026-NR86406, CLEANSTART-2026-YF88900, DEBIAN-CVE-2026-12816 and 2 more.