CVE-2026-18036

HIGHPre-NVD 8.28.2
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This high-severity CVE scores 8.2 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3% (21st percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source

Also known asEUVD-2026-91317 (ENISA EUVD) · GHSA-frjj-v5w4-68pc (GitHub Security Advisories)Source: ENISA EUVD

8.2EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 8.2Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS
8.2
EG Score
8.2HIGHmedium confidence
EG Risk
37
EG Risk 37/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity82% × 45%
Impact severity (EG Severity): CVSS 8.2 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.3% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
21st
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (8.2): severity, escalated by confirmed exploitation. This CVE's 8.2 is its impact severity (EG Severity), not escalated.

EG Severity
8.2 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-10). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

October 2, 2026

Last Modified

October 2, 2026

Advisory Details (2)

Auto-updated Oct 2, 2026
Patch available. Sources: github_commit.
GitHub commit

commit 9c9ad88b6003 (bcgit/bc-java)

Fix landed in bcgit/bc-java commit 9c9ad88b6003 — awaiting tagged release

https://github.com/bcgit/bc-java/commit/9c9ad88b6003bb6230d2434bd892cc1e95b294e4
Web page

CVE‐2026‐18036 · bcgit/bc-java Wiki · GitHub

https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9018036

Vendor Advisories for CVE-2026-18036(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
bouncycastle1.72-2 ... 1.86-1 (6 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
bouncycastle1.80-3, 1.86-1
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
bouncycastle1.80-3
  • every version up to 1.86-1: fixed in 1.86-1
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 33× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 1 repeat row among the latest 92 is merged into the row it repeats.

  1. 2026-11-12 16:33 UTCEPSS rescoreEPSS 0.3% · 21st percentile
  2. 2026-11-11 16:38 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  3. 2026-11-11 03:53 UTCEchelonGraph re-scored
  4. 2026-11-11 03:53 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  5. 2026-11-10 16:42 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  6. 2026-11-09 16:34 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  7. 2026-11-08 16:38 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  8. 2026-11-07 16:38 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  9. 2026-11-06 16:37 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  10. 2026-11-05 16:37 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  11. 2026-11-04 16:35 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  12. 2026-11-03 20:15 UTCEchelonGraph re-scored
  13. 2026-11-03 20:15 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  14. 2026-11-03 16:47 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  15. 2026-11-02 16:44 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  16. 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  17. 2026-10-30 16:33 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  18. 2026-10-29 16:32 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  19. 2026-10-28 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  20. 2026-10-27 20:53 UTCEchelonGraph re-scored
  21. 2026-10-27 20:53 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  22. 2026-10-27 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  23. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  24. 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.3% · 20th percentile
  25. 2026-10-25 14:45 UTCEchelonGraph re-scored
Show 66 more
  1. 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  2. 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  3. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  4. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  5. 2026-10-20 19:07 UTCEchelonGraph re-scored
  6. 2026-10-20 19:07 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  7. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  8. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  9. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  10. 2026-10-18 03:59 UTCEchelonGraph re-scored
  11. 2026-10-17 17:54 UTCEchelonGraph re-scored
  12. 2026-10-17 17:54 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  13. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  14. 2026-10-16 16:40 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  15. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  16. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  17. 2026-10-13 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  18. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  19. 2026-10-12 16:28 UTCEchelonGraph re-scored
  20. 2026-10-11 20:08 UTCEchelonGraph re-scored
  21. 2026-10-11 18:57 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  22. 2026-10-11 17:20 UTCEchelonGraph re-scored
  23. 2026-10-11 14:52 UTCEchelonGraph re-scored
  24. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  25. 2026-10-11 07:33 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  26. 2026-10-10 20:07 UTCEchelonGraph re-scored
  27. 2026-10-10 20:07 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  28. 2026-10-10 19:59 UTCEPSS rescoreEPSS 0.3% · 19th percentile
  29. 2026-10-10 08:45 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  30. 2026-10-09 21:21 UTCEchelonGraph re-scored
  31. 2026-10-09 21:21 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  32. 2026-10-09 20:06 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  33. 2026-10-09 09:58 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  34. 2026-10-08 22:32 UTCEchelonGraph re-scored
  35. 2026-10-08 22:32 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  36. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  37. 2026-10-08 10:59 UTCEchelonGraph re-scored
  38. 2026-10-08 10:59 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  39. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  40. 2026-10-07 23:36 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  41. 2026-10-07 12:13 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  42. 2026-10-07 00:51 UTCEchelonGraph re-scored
  43. 2026-10-07 00:50 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  44. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  45. 2026-10-06 13:26 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  46. 2026-10-06 02:04 UTCEchelonGraph re-scored
  47. 2026-10-06 02:03 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  48. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  49. 2026-10-05 14:40 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  50. 2026-10-05 03:18 UTCEchelonGraph re-scored
  51. 2026-10-05 03:18 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  52. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  53. 2026-10-04 15:56 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  54. 2026-10-04 04:33 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  55. 2026-10-03 17:11 UTCEchelonGraph re-scored
  56. 2026-10-03 17:10 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  57. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.3% · 18th percentile
  58. 2026-10-03 05:45 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  59. 2026-10-02 18:20 UTCEchelonGraph re-scored
  60. 2026-10-02 18:20 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  61. 2026-10-02 17:47 UTCEchelonGraph re-scored
  62. 2026-10-02 17:47 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  63. 2026-10-02 14:45 UTCGHSA enrichmentGHSA-frjj-v5w4-68pc · GitHub severity HIGH
  64. 2026-10-02 08:27 UTCEchelonGraph re-scored
  65. 2026-10-02 07:57 UTCEchelonGraph re-scoredFirst assessed: 8.2 HIGH
  66. 2026-10-02 07:55 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-18036?
CVE-2026-18036 is a high-severity vulnerability; its CVE record was published on October 2, 2026. 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…
When was the CVE record for CVE-2026-18036 published?
The CVE record for CVE-2026-18036 was published on October 2, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 2, 2026; the record at its source may have been updated since.
Is CVE-2026-18036 actively exploited?
CVE-2026-18036 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (21st percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-18036?
CVE-2026-18036 has a CVSS base score of 8.2 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-18036?
A fix for CVE-2026-18036 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-18036 are linked in the Vendor Advisories panel on this page.

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