Vulnerability · Published Oct 2, 2026 · Assigned by bcorg
CVE-2026-17508Password-based KDF cost parameters honoured unbounded from untrusted input across the remaining PBE entry points
Medium 5.3
In plain English
A medium-severity resource allocation without limits in BC-FJA from Legion of the Bouncy Castle Inc.. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
In Bouncy Castle for Java before 1.86, several password-based key derivation entry points ran the KDF with cost parameters taken from the untrusted input being processed, without bounding them, so a small input could dictate an arbitrary amount of work before any password or integrity check could reject it. The affected paths are the RFC 9579 PBMAC1 MAC calculator builders, which took the PBKDF2 iteration count and derived-key length straight out of PBMAC1Params (JcePBMac1CalculatorBuilder, and PKCS12PBEUtils.createPBMac1Calculator reached from PKCS12PfxPdu.isMacValid); the scrypt parallelization parameter p in the PKCS#8 and PKCS#12 cost guards, which bounded only the cost parameter N and the block size r even though the scratch buffer scales with r times p, so the configured memory ceiling could be evaded entirely; the raw JCA PBKDF2 provider (org.bouncycastle.jcajce.provider.symmetric.PBEPBKDF2); and the bcrypt round count read from an encrypted OpenSSH v1 private key's own kdfoptions. Each now bounds the parameter before deriving, in line with the caps already applied elsewhere in the tree, with the OpenSSH round count configurable through the new org.bouncycastle.openssh.max_rounds property. This completes the bounding begun in 1.85 for the PKCS#8 / PBES2 decryptors (CVE-2026-15055). This issue also affects Bouncy Castle for Java LTS before 2.73.13, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | bouncycastle | no fix listed | DEBIAN-CVE-2026-17508 |
| Debian:13 | bouncycastle | no fix listed | DEBIAN-CVE-2026-17508 |
| Debian:14 | bouncycastle | 1.86-1 | DEBIAN-CVE-2026-17508 |
| Ubuntu:26.04:LTS | bouncycastle | no fix listed | UBUNTU-CVE-2026-17508 |
| Ubuntu:26.10 | bouncycastle | no fix listed | UBUNTU-CVE-2026-17508 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Legion of the Bouncy Castle Inc. | BC-JAVA | 0 – before 1.86 |
| Legion of the Bouncy Castle Inc. | BC-JAVA | 0 – before 1.86 |
| Legion of the Bouncy Castle Inc. | BC-LTS-JAVA | 2.73.0 – before 2.73.13 |
| Legion of the Bouncy Castle Inc. | BC-LTS-JAVA | 2.73.0 – before 2.73.13 |
| Legion of the Bouncy Castle Inc. | BC-FJA | 1.0.0 – before 1.0.132.0.0 – before 2.0.132.1.0 – before 2.1.13 |
Weakness: CWE-770 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber
References
- https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9017508 vendor-advisory
- https://github.com/bcgit/bc-java/commit/882fdab53f6c4c150a5d6a4e6ef1fc05d382385a patch
- https://github.com/bcgit/bc-java/commit/442393bf187c914b1e66fbed4fab532a1fe06c6a patch
- https://github.com/bcgit/bc-java/commit/20ed9e203caec91d25cd386ceb6d364e9b068f67 patch
- https://github.com/bcgit/bc-java/commit/766a31026ac24ed3c6cad8662058ba450c338da1 patch
- https://github.com/bcgit/bc-java/commit/e72bc0681ff4227fced912ef7394daf7b7d57bb3 patch
- https://github.com/bcgit/bc-java/commit/480d878aa6f7dc8b20403064f304bbe0decbbb1a patch