MediumCVE-2026-17508

    Legion of the Bouncy Castle BC-FJA: Allocation of Resources Without Limits or Throttling (CVE-2026-17508)

    Published Last modified Sources: BSI, CVE.org, SUSE

    What is affected, what to do

    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.

    Update Legion of the Bouncy Castle BC-JAVA to version 1.86, Legion of the Bouncy Castle BC-LTS-JAVA to version 2.73.13, Legion of the Bouncy Castle BC-FJA to version 1.0.13.

    Affected
    • Legion of the Bouncy Castle BC-JAVA lt *..1.86
    • Legion of the Bouncy Castle BC-LTS-JAVA lt 2.73.0..2.73.13
    • Legion of the Bouncy Castle BC-FJA lt 1.0.0..1.0.13
    • Legion of the Bouncy Castle BC-FJA lt 2.0.0..2.0.13
    • Legion of the Bouncy Castle BC-FJA lt 2.1.0..2.1.13
    Fixed in
    • Legion of the Bouncy Castle BC-JAVA 1.86
    • Legion of the Bouncy Castle BC-LTS-JAVA 2.73.13
    • Legion of the Bouncy Castle BC-FJA 1.0.13
    • Legion of the Bouncy Castle BC-FJA 2.0.13
    • Legion of the Bouncy Castle BC-FJA 2.1.13

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    5.3

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: Vendor (CNA), CVSS v4

    5.3

    CVSS v4

    Severity Medium on the scale from 0 to 10.

    Source: BSI, CVE.org, SUSE

    0.4 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 36.1

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    66.93 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    5.3 Methodology
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    5.3
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.4 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    36.1
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 2 October 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-770

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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).

    Source: BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), suse_csaf

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    Legion of the Bouncy Castle Inc.BC-FJA
    • 2.0.0 – < 2.0.13
    • 2.1.0 – < 2.1.13
    • 1.0.0 – < 1.0.13
    • 2.0.13
    • 2.1.13
    • 1.0.13
    Legion of the Bouncy Castle Inc.BC-JAVA
    • < 1.86
    • 1.86
    Legion of the Bouncy Castle Inc.BC-LTS-JAVA
    • 2.73.0 – < 2.73.13
    • 2.73.13
    Open SourceBouncy Castle bc-csharp
    • < 2.7.0
    • 2.7.0
    Open SourceBouncy Castle for Java
    • < 1.86
    • 1.86
    Open SourceBouncy Castle for Java FIPS
    • < 1.0.13
    • < 2.0.13
    • < 2.1.13
    • 1.0.13
    • 2.0.13
    • 2.1.13
    Open SourceBouncy Castle for Java LTS
    • < 2.73.13
    • 2.73.13

    Vendors and products

    Weakness classes (CWE)

    • CWE-770Allocation of Resources Without Limits or Throttling

      Base

      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.

      Entry at MITRE CWE-770

    References & sources

    • github.combcgit/bc-java/wiki/CVE‐2026‐17508Vendor advisory
    • github.combcgit/bc-java/commit/882fdab53f6c4c150a5d6a4e6ef1fc05d382385aPatch
    • github.combcgit/bc-java/commit/442393bf187c914b1e66fbed4fab532a1fe06c6aPatch
    • github.combcgit/bc-java/commit/20ed9e203caec91d25cd386ceb6d364e9b068f67Patch
    • github.combcgit/bc-java/commit/766a31026ac24ed3c6cad8662058ba450c338da1Patch
    • github.combcgit/bc-java/commit/e72bc0681ff4227fced912ef7394daf7b7d57bb3Patch
    • github.combcgit/bc-java/commit/480d878aa6f7dc8b20403064f304bbe0decbbb1aPatch

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-17508","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-10-02T17:43:15.561288Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    2. Receivedbcorg

      CVSS V4.0: AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber

      Weakness type: CWE-770

      Description added or changed

      Show 11 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      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).
      CVSSadded
      —
      AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
      Weakness type (CWE)added
      —
      CWE-770
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/17xxx/CVE-2026-17508.json">CVE-2026-17508</a>
      Referenceadded
      —
      https://github.com/bcgit/bc-java/commit/20ed9e203caec91d25cd386ceb6d364e9b068f67
      Referenceadded
      —
      https://github.com/bcgit/bc-java/commit/442393bf187c914b1e66fbed4fab532a1fe06c6a
      Referenceadded
      —
      https://github.com/bcgit/bc-java/commit/480d878aa6f7dc8b20403064f304bbe0decbbb1a
      Referenceadded
      —
      https://github.com/bcgit/bc-java/commit/766a31026ac24ed3c6cad8662058ba450c338da1
      Referenceadded
      —
      https://github.com/bcgit/bc-java/commit/882fdab53f6c4c150a5d6a4e6ef1fc05d382385a
      Referenceadded
      —
      https://github.com/bcgit/bc-java/commit/e72bc0681ff4227fced912ef7394daf7b7d57bb3
      Referenceadded
      —
      https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9017508

      Source identifier: 91579145-5d7b-4cc5-b925-a0262ff19630

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