CVE-2026-17508
Received Received - Intake

Denial of Service in Bouncy Castle for Java

Publication date: 2026-10-02

Last updated on: 2026-10-02

Assigner: bcorg

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).

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Meta Information

Published
2026-10-02
Last Modified
2026-10-02
Generated
2026-10-02
AI Q&A
2026-10-02
EPSS Evaluated
N/A
NVD
CVE-2026-17508
EUVD
EUVD-2026-91236

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
bouncy_castle bouncy_castle_java 1.85
bouncy_castle bouncy_castle_java to 1.86 (exc)
bouncy_castle bouncy_castle_java_lts to 2.73.13 (exc)
bouncy_castle bouncy_castle_java_fips to 2.1.13 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Attack-Flow Graph

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Executive Summary

CVE-2026-17508 is a pre-authentication CPU denial-of-service (DoS) vulnerability in Bouncy Castle for Java. It affects password-based key derivation functions (KDFs) that process untrusted input without prior authentication. Attackers can manipulate cost parameters like iteration counts or key lengths to force excessive computational work, causing CPU exhaustion before password or integrity checks. Affected components include PBKDF2, scrypt, PBMAC1, and bcrypt implementations.

Detection Guidance

To detect this vulnerability, check if your Bouncy Castle Java library version is below 1.86, BC-LTS before 2.73.13, or BC-FJA before specified bcpkix-fips versions. Use commands like 'mvn dependency:tree' or 'gradle dependencies' to inspect library versions in your project.

Impact Analysis

This vulnerability allows attackers to perform DoS attacks by sending maliciously crafted inputs that trigger unbounded CPU or memory usage. Systems using vulnerable Bouncy Castle versions for cryptographic operations could experience degraded performance, crashes, or service unavailability. Attackers may exploit this without authentication, making it particularly dangerous for servers handling cryptographic operations.

Compliance Impact

This vulnerability primarily enables denial-of-service (DoS) attacks by allowing attackers to force excessive CPU or memory usage during key derivation before authentication. While not directly violating GDPR or HIPAA, such attacks could disrupt systems handling sensitive data, potentially leading to unauthorized access or service disruptions that may violate compliance requirements for availability and security controls.

Mitigation Strategies

Upgrade Bouncy Castle Java to version 1.86 or later, BC-LTS to 2.73.13 or later, and BC-FJA to the specified bcpkix-fips versions. For OpenSSH keys, set the 'org.bouncycastle.openssh.max_rounds' property to limit bcrypt rounds. Monitor logs for exceptions like OperatorCreationException or IllegalArgumentException during key derivation.

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