{"answers":{"affected":"It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-63573 in the wild and no public exploit code.","fix":"No fix has been published for CVE-2026-63573 yet. Limit exposure of the affected software until one is available.","what":"CVE-2026-63573 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-2026-63573 and fix it if it is affected.\n\nWhat it is: CVE-2026-63573 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-2026-63573 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-2026-63573/ (Markdown: https://insights.sbomify.com/CVE-2026-63573/index.md)","id":"CVE-2026-63573","markdown":"https://insights.sbomify.com/CVE-2026-63573/index.md","name":"CVE-2026-63573","record":{"aliases":["GHSA-xx4m-xv2j-xx6g"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["data_read"],"network_reachable":"yes","non_default_config":false,"product_category":"C# cryptography library","requires_auth":"none","summary":"A Bleichenbacher padding oracle in the Bouncy Castle C# library allows attackers to decrypt CMS messages by distinguishing invalid padding errors.","user_interaction":"not_required","vuln_class":"other"},"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:H/VI:N/VA:N/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-203","name":"Observable Discrepancy"}],"description":"Observable discrepancy in the CMS RSA PKCS#1 v1.5 key-transport unwrap (KeyTransRecipientInformation.UnwrapKey) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote attacker who holds a captured CMS EnvelopedData message, and who can submit many modified messages to an application that decrypts them with the recipient's RSA private key and reveals how decryption failed, to recover the captured message's content-encryption key and so its content, via a Bleichenbacher-style adaptive chosen-ciphertext attack, because a key-transport ciphertext with invalid PKCS#1 v1.5 padding is rejected during unwrap with a distinct \"bad padding in message.\" CmsException instead of being replaced by a random key, so it can be told apart from a correctly padded ciphertext, which fails only later at content 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":"Bleichenbacher padding oracle in CMS RSA PKCS#1 v1.5 key-transport unwrap","id":"CVE-2026-63573","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":null,"product":null,"products":[],"type":"other","year":"2026"},"n_packages":0,"n_references":3,"next":{"headline":"Unbounded allocation from OpenPGP signature and user attribute subpacket lengths","id":"CVE-2026-63574"},"packages":[],"prev":{"headline":"Unbounded MAC and bag-decryption iteration counts when loading PKCS#12 files","id":"CVE-2026-63572"},"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":"A Bleichenbacher padding oracle in the Bouncy Castle C# library allows attackers to decrypt CMS messages by distinguishing invalid padding errors.","url":"https://insights.sbomify.com/CVE-2026-63573/"}