CVE-2026-12860 RSA PKCS#1 verification skips last two hash bytes in NULL-omitted path
Attackers can bypass RSA PKCS#1 signature verification in Bouncy Castle for Java by exploiting a flaw that skips hash bytes in specific paths.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-12860?
CVE-2026-12860 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, RSA PKCS#1 verification skips last two hash bytes in NULL-omitted path. This issue also affects Bouncy Castle for Java LTS before 2.73.12.
Weakness: CWE-347
Which versions are affected by CVE-2026-12860?
It affects 2 products.
Products include Bouncycastle Bc-Java, Bouncycastle Bouncy Castle for Java Lts.
How do I fix CVE-2026-12860?
Upgrade to a fixed version.
Is CVE-2026-12860 being exploited?
There is no known exploitation of CVE-2026-12860 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-GU33200, CLEANSTART-2026-IW98421, CLEANSTART-2026-LA60535, CLEANSTART-2026-SW32419, CLEANSTART-2026-TN87218, DEBIAN-CVE-2026-12860 and 2 more.