CVE-2026-97873 Legacy PBES1 and PKCS#12 PBE iteration count honoured unbounded in the raw JCA provider
Attackers can cause denial of service by supplying unbounded iteration counts in PKCS#12 or PBES1 parameters, forcing excessive computation during key derivation.
- 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-2026-97873?
CVE-2026-97873 is a medium-severity denial of service vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA, published on 3 Oct 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 1.86, the raw JCA provider's legacy PBES1 (PKCS#5 scheme 1) and PKCS#12 PBE families ran their password-based key derivation with an iteration count taken from untrusted input without bounding it, so a small input could dictate an arbitrary amount of work before anything could be verified. The AlgorithmParameters implementations (PKCS12PBE and its object identifier aliases, and PBKDF1) accepted any count from an encoded PKCS12PBEParams or PBEParameter, narrowing a value beyond the int range with intValue(), and every Cipher, Mac and SecretKeyFactory in these families derived with whatever count it was given, including one decoded by another provider's AlgorithmParameters, as when javax.crypto.EncryptedPrivateKeyInfo.getKeySpec() decrypts a PKCS#12 PBE-protected private key with BC. Both the parameter parse and the derivations now reject a negative or over-limit count under the org.bouncycastle.pbe.max_iteration_count property (default 10,000,000) that already bounded PBKDF2 (CVE-2026-17508), and the parse rejects a count beyond the int range rather than narrowing it. This issue also affects Bouncy Castle for Java LTS before 2.73.13.
Weakness: CWE-770
Which versions are affected by CVE-2026-97873?
How do I fix CVE-2026-97873?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-97873 being exploited?
There is no known exploitation of CVE-2026-97873 in the wild and no public exploit code.
Sources
Also known as CLEANSTART-2026-MT03489, CLEANSTART-2026-TA59206, DEBIAN-CVE-2026-97873, GHSA-78x9-mjv2-rr3v, UBUNTU-CVE-2026-97873.