CVE-2026-18036
- Source
- https://cve.org/CVERecord?id=CVE-2026-18036
- Import Source
- https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-18036.json
- JSON Data
- https://api.test.osv.dev/v1/vulns/CVE-2026-18036
- Downstream
DEBIAN (1)
openSUSE (1)
SUSE (1)
UBUNTU (1)
- Related
- Published
- 2026-10-02T07:54:16Z
- Modified
- 2026-10-22T16:16:12Z
- Severity
-
- 8.2 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/U:Amber CVSS Calculator
- 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.
- Database specific
{ "cna_assigner": "bcorg", "cwe_ids": [ "CWE-208" ], "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/18xxx/CVE-2026-18036.json" }- References
-
- https://www.bouncycastle.org/download/bouncy-castle-java/
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/18xxx/CVE-2026-18036.json
- https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9018036
- https://nvd.nist.gov/vuln/detail/CVE-2026-18036
- https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4
- https://github.com/bcgit/bc-java
Affected packages
Git / github.com/bcgit/bc-java
Affected ranges
- Type
- GIT
- Repo
- https://github.com/bcgit/bc-java
- Events
- Database specific
-
Show details
{ "extracted_events": [ { "range": [ { "introduced": "1.73" }, { "fixed": "1.86" } ], "source": "AFFECTED_FIELD", "strategy": "StandardRange" }, { "range": [ { "fixed": "9c9ad88b6003bb6230d2434bd892cc1e95b294e4" } ], "source": "REFERENCES_COMMIT" } ] }
Database specific
source
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-18036.json"
vanir_signatures
[
{
"deprecated": false,
"digest": {
"function_hash": "99335319624403829571532364691283783230",
"length": 80
},
"id": "CVE-2026-18036-6c3b501b",
"signature_type": "Function",
"signature_version": "v1",
"source": "https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4",
"target": {
"file": "core/src/main/java/org/bouncycastle/pqc/math/ntru/Polynomial.java",
"function": "mod3"
}
},
{
"deprecated": false,
"digest": {
"line_hashes": [
"15680412856031196787990673747701544330",
"115195829514276812792161094455006121373",
"164844410459406839810959913402674964799",
"222868103469363150237900034007207071107",
"40826237893040310746607121531876280739",
"57905628113648477858215661961515089202",
"244105881433912381496373469733194077588",
"102028569115762235449062903247799187456",
"11974242969275831223829926742786449408",
"300004068565516473747058896877486146916",
"191205219460096188324818343340589241553",
"166215844114616201005845394545431673852",
"11004915667868475128195291634305365923",
"213863427817204038271627700028078091036"
],
"threshold": 0.9
},
"id": "CVE-2026-18036-7897e6bf",
"signature_type": "Line",
"signature_version": "v1",
"source": "https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4",
"target": {
"file": "core/src/main/java/org/bouncycastle/pqc/math/ntru/Polynomial.java"
}
},
{
"deprecated": false,
"digest": {
"function_hash": "247125669952043661407303634151120519235",
"length": 71
},
"id": "CVE-2026-18036-a4c04878",
"signature_type": "Function",
"signature_version": "v1",
"source": "https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4",
"target": {
"file": "core/src/main/java/org/bouncycastle/pqc/math/ntru/Polynomial.java",
"function": "modQ"
}
},
{
"deprecated": false,
"digest": {
"function_hash": "323429808407840888333551253031526739826",
"length": 78
},
"id": "CVE-2026-18036-a8ee432e",
"signature_type": "Function",
"signature_version": "v1",
"source": "https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4",
"target": {
"file": "core/src/main/java/org/bouncycastle/pqc/math/ntru/Polynomial.java",
"function": "mod3"
}
},
{
"deprecated": false,
"digest": {
"line_hashes": [
"25805128286082913654666991975508356010",
"150087098969303988676877102802038118131",
"61064119935604497318036595237002628304",
"212318202281250366308548230465613191156",
"148899749075524412971792461938718627083"
],
"threshold": 0.9
},
"id": "CVE-2026-18036-b434da01",
"signature_type": "Line",
"signature_version": "v1",
"source": "https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4",
"target": {
"file": "core/src/main/java/org/bouncycastle/pqc/crypto/ntru/NTRUSampling.java"
}
},
{
"deprecated": false,
"digest": {
"function_hash": "26627069544171511887990067220854408135",
"length": 53
},
"id": "CVE-2026-18036-d1ebf223",
"signature_type": "Function",
"signature_version": "v1",
"source": "https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4",
"target": {
"file": "core/src/main/java/org/bouncycastle/pqc/crypto/ntru/NTRUSampling.java",
"function": "mod3"
}
}
]
vanir_signatures_modified
"2026-10-22T16:16:12Z"