TI-2026-67470 Aliases CVE-2026-18040 GHSA-rxw8-22c7-wgq6

HQC leaks private key information through secret-indexed GF(2^8) tables and a secret-dependent fixed-weight sampler

LOW 25CWE-208Published 2026-10-03 · Updated 2026-10-05

Key facts

Attack vector: Local
Privileges required: None
User interaction: None
Attack complexity: High
Attack requirements: Present
Impact type: Information disclosure
Confidentiality · integrity · availability: High · None · None
Fix status: Partial Red Hat: 16 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-208.

Summary

In Bouncy Castle for Java before 1.86, HQC leaked secret-derived data through two side channels: its GF(2^8) arithmetic used lookup tables indexed by field elements, making the cache line touched a function of the operand, and its fixed-weight support sampler left its duplicate scan as soon as a collision was found and stored accepted positions at a secret index. Both run on secret inputs during encapsulation and decapsulation, and the sampler re-expands the secret key from its seed on every decapsulation, so an attacker able to observe cache behaviour or decapsulation timing can recover information about the HQC private key. The field arithmetic is now table-free and the sampler branch-free within a batch of candidates, with output and randomness consumption unchanged.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00107 1st percentileScored 2026-11-07

Fix Partial BC-JAVA (Legion of the Bouncy Castle Inc.): 1.86Red Hat: 16 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Legion of the Bouncy Castle Inc.	BC-JAVA	1.73 to before 1.86	1.86	Patch available	CNA

BC-JAVA VendorLegion of the Bouncy Castle Inc. Affected 1.73 to before 1.86 Fixed in 1.86 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPE	Versions	Role	Vendor
cpe:2.3:a:bouncycastle:bc-java::::::::	—	—	Legion of the Bouncy Castle Inc.

cpe:2.3:a:bouncycastle:bc-java:*:*:*:*:*:*:*:* Versions — — ·Legion of the Bouncy Castle Inc.

Remediation

Fix · CNA BC-JAVA (Legion of the Bouncy Castle Inc.) Fixed in 1.86

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

Release · 2026-10-03
Legion of the Bouncy Castle BC-JAVA 1.86
11 records Highest priority Priority MEDIUM 4 MEDIUM, 7 LOW
Other records, highest priority first
- TI-2026-67477 MLS external commit can remove an arbitrary group memberPriority MEDIUM 43
- TI-2026-67476 PKIXCertPathReviewer does not apply X.509 name constraints to the target certificatePriority MEDIUM 43
- TI-2026-67475 CMS AuthenticatedData exposes attacker-inserted authAttrs when digestAlgorithm is absentPriority MEDIUM 42
Show all 11 records →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
OpenShift Developer Tools and Services	Affected	No fix yet: Fix deferred
Red Hat AMQ Broker 7	Affected	No fix yet: Fix deferred
Red Hat Ansible Automation Platform 2	Affected	No fix yet: Fix deferred
Red Hat Build of Keycloak	Affected	No fix yet: Fix deferred
Red Hat Fuse 7	Affected	No fix yet: Fix deferred
Red Hat JBoss Enterprise Application Platform 7	Affected	No fix yet: Fix deferred
Red Hat JBoss Enterprise Application Platform 8	Affected	No fix yet: Fix deferred
Red Hat JBoss Enterprise Application Platform Expansion Pack	Affected	No fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)	Affected	No fix yet: Fix deferred
Red Hat OpenShift Dev Spaces	Affected	No fix yet: Fix deferred
Red Hat Satellite 6	Affected	No fix yet: Fix deferred
Red Hat Single Sign-On 7	Affected	No fix yet: Fix deferred
Red Hat build of Apache Camel 4 for Quarkus 3	Affected	No fix yet: Fix deferred
Red Hat build of Apache Camel for Spring Boot 4	Affected	No fix yet: Fix deferred
Red Hat build of Apicurio Registry 3	Affected	No fix yet: Fix deferred
Red Hat build of Quarkus	Affected	No fix yet: Fix deferred

Timeline

2026-10-03 Threatist record created from CVE-2026-18040
2026-10-03 Alias added: GHSA-rxw8-22c7-wgq6
2026-10-04 Priority changed: MEDIUM → LOW
2026-10-05 CISA SSVC decision points changed
2026-10-16 Affected versions changed · Red Hat
2026-10-16 CVSS score added · Red Hat

References

Patch 1

https://github.com/bcgit/bc-java/commit/283acd81048ec9e951032525279d3b58aaf0bb03

Advisory 1

https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9018040

TI-2018-15967 Legion of the Bouncy Castle Legion of the Bouncy Castle Java Cryptography APIs 1.58 up to… CVSS 3.1CRITICAL 9.8
TI-2017-09736 BouncyCastle JCE TLS Bleichenbacher/ROBOT CVSS 3.0HIGH 7.5
TI-2026-42545 MTI/A0 DH agreement exponentiates unvalidated peer value CVSS 4.0CRITICAL 9.3
TI-2026-42533 JSSE hostname verifier CN-fallback enabled by default despite documented opt-in CVSS 4.0CRITICAL 9.3
TI-2026-41816 Stapled OCSP response accepted without binding to the checked certificate CVSS 4.0CRITICAL 9.3
TI-2026-07701 Name Constraints bypass via trailing dot in rfc822Name and URI CVSS 4.0CRITICAL 9.3

See all 109 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences