CVE-2026-97873: Legacy PBES1 and PKCS#12 PBE iteration count honoured unbounded in the raw JCA provider

Severity: medium (CVSS 5.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-03 · updated 2026-10-06
Weakness: CWE-770

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.

Affected products

Legion of the Bouncy Castle Inc. BC-JAVA: before 1.86 — fixed in 1.86
Legion of the Bouncy Castle Inc. BC-LTS-JAVA: from 2.73.0 before 2.73.13 — fixed in 2.73.13

How to fix

Upgrade to a fixed version: Legion of the Bouncy Castle Inc. BC-JAVA 1.86; Legion of the Bouncy Castle Inc. BC-LTS-JAVA 2.73.13. Check the vendor advisory for mitigations.

References

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