{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-15999 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2026-15999 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-15999 is a high-severity vulnerability in Legion of the Bouncy Castle Inc. bc-csharp, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-15999 and fix it if it is affected.\n\nWhat it is: CVE-2026-15999 is a high-severity vulnerability in Legion of the Bouncy Castle Inc. bc-csharp, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-15999 in the wild and no public exploit code.\n\nAffected product: Legion of the Bouncy Castle Inc. bc-csharp. No package-level version data is available, so check the vendor advisory linked from the reference page.\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-15999/ (Markdown: https://insights.sbomify.com/CVE-2026-15999/index.md)","id":"CVE-2026-15999","markdown":"https://insights.sbomify.com/CVE-2026-15999/index.md","name":"CVE-2026-15999","record":{"aliases":["GHSA-499v-wjw6-fvpx"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["data_modify","security_bypass"],"network_reachable":"yes","non_default_config":false,"product_category":"C# cryptography library","requires_auth":"none","summary":"An on-path attacker can modify AES-CCM encrypted content without detection due to improper tag length validation in the Bouncy Castle C# library.","user_interaction":"not_required","vuln_class":"security_feature_bypass"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"bcorg","cpe":[{"product":"bc-csharp","vendor":"bouncycastle"}],"cvss":{"score":8.2,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-354","name":"Improper Validation of Integrity Check Value"}],"description":"Improper validation of integrity check value in the AES-CCM implementation (CcmParameters and CcmBlockCipher) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an on-path attacker to modify CCM-encrypted content without detection via an AlgorithmIdentifier whose CCMParameters declare an authentication tag (aes-ICVlen) of zero or another length outside the RFC 5084 set, because CcmParameters accepted any value and CcmBlockCipher validated the tag length only when encrypting, so decryption compared a zero-length or very short tag. Affected paths include ParameterUtilities.GetCipherParameters, used by CmsEnvelopedData and CmsEnvelopedDataParser for EnvelopedData encrypted with AES-CCM, and any caller passing an unchecked tag length to CcmBlockCipher for decryption.","ecosystems":[],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":false,"headline":"AES-CCM decryption accepts zero or out-of-range tag length, bypassing authentication","id":"CVE-2026-15999","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"security_feature_bypass","year":"2026"},"n_packages":0,"n_references":3,"next":{"headline":"KCcmBlockCipher (DSTU 7624 CCM) tag not bound to nonce when no associated data is used","id":"CVE-2026-16000"},"packages":[],"prev":{"headline":"Native ARM SHA3 / SHAKE `restoreFullState` fails to detect size_t underflow in a crafted encoded state","id":"CVE-2026-15997"},"products":["bc-csharp"],"published":"2026-10-02","related":[{"cvss_score":9.1,"headline":"MTI/A0 DHAgreement does not validate the peer's ephemeral value","id":"CVE-2026-63569","kev_date_added":null,"published":"2026-10-02"},{"cvss_score":8.7,"headline":"Unbounded ASN.1 nesting depth causes process-terminating stack overflow","id":"CVE-2026-103600","kev_date_added":null,"published":"2026-10-02"},{"cvss_score":8.7,"headline":"Unbounded HSS public key level count allows huge array allocation during signature verification","id":"CVE-2026-103603","kev_date_added":null,"published":"2026-10-02"},{"cvss_score":8.7,"headline":"Quadratic-time escaping when converting X.509 distinguished names to strings","id":"CVE-2026-103604","kev_date_added":null,"published":"2026-10-02"},{"cvss_score":8.7,"headline":"KCcmBlockCipher (DSTU 7624 CCM) tag not bound to nonce when no associated data is used","id":"CVE-2026-16000","kev_date_added":null,"published":"2026-10-02"},{"cvss_score":8.7,"headline":"DTLS handshake reassembler allocates buffer from unchecked 24-bit length","id":"CVE-2026-63566","kev_date_added":null,"published":"2026-10-02"},{"cvss_score":8.7,"headline":"Unbounded CMP/CRMF password-based MAC iteration count allows CPU exhaustion","id":"CVE-2026-63568","kev_date_added":null,"published":"2026-10-02"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-10-02","vendors":["Legion of the Bouncy Castle Inc."]},"summary":"An on-path attacker can modify AES-CCM encrypted content without detection due to improper tag length validation in the Bouncy Castle C# library.","url":"https://insights.sbomify.com/CVE-2026-15999/"}