{"schema":"threatline.record/2","record":{"id":"CVE-2026-18036","aliases":[],"summary":"NTRU leaks private key information by reducing secret values with a non-constant-time integer division","details":"In Bouncy Castle for Java before 1.86, NTRU reduced secret values with the % operator in three helpers whose reference implementations are deliberately division-free, so each reduction was carried out by an integer division whose latency depends on the secret operand. Polynomial.modQ divided by a variable divisor, which a compiler cannot strength-reduce to a multiply the way it can a constant one, so it emitted a division on every call including on the decapsulation path where the dividend derives from the private key; Polynomial.mod3 and NTRUSampling.mod3 divided the secret key polynomials f and g during key generation, the message polynomials r and m during encapsulation, and coefficients recovered during decapsulation. An attacker able to measure that timing can recover information about the NTRU private key. modQ now masks, which is exact because q is always a power of two, and mod3 uses the reference implementation's division-free fold and select; the results are unchanged.","categories":["Unclassified"],"product":"BC-JAVA","vendor":"Legion of the Bouncy Castle Inc.","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-18036","source_modified_at":"2026-10-02T17:42:56.393Z","fetched_at":"2026-10-23T18:52:38.922436Z","product":"BC-JAVA","vendor":"Legion of the Bouncy Castle Inc.","versions":[{"status":"affected","version":"1.73","lessThan":"1.86","versionType":"maven"}],"defaultStatus":"unaffected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-18036","source_modified_at":"2026-10-02T17:42:56.393Z","fetched_at":"2026-10-23T18:52:38.922436Z","package":{"name":"BC-JAVA","ecosystem":null},"version":"1.86","basis":"first unaffected version stated in the CVE record"}],"cvss":8.2,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00282,"percentile":0.19639,"score_date":"2026-10-23"},"published_at":"2026-10-02T07:54:16.063Z","modified_at":"2026-10-02T17:42:56.393Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-18036","fetched_at":"2026-10-23T18:52:38.922436Z","source_modified_at":"2026-10-02T17:42:56.393Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-18036","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9018036","tags":["vendor-advisory"]},{"source":"CVE List","url":"https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4","tags":["patch"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"partial","assessed_at":"2026-10-02T17:42:43.345821Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-02T17:42:56.393Z","content_hash":"0d0db3818e7be7ae21153017816879b23adc4c80344dafe58401151b0400c4e0"}}