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CVE Record

CVE-2026-5598: Non-constant time comparisons risk private key leakage in FrodoKEM.

Covert timing channel vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA core on all (core modules). This vulnerability is associated with program files FrodoEngine.Java. This issue affects BC-JAVA: from 1.71 before 1.80.2, from 1.81 before 1.81.1, from 1.82 before 1.84.

HighCVSS 8.9Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

BC-JAVA’s FrodoKEM code used timing-sensitive comparisons that may reveal private key information. The issue is high severity because vulnerable cryptographic code can undermine confidentiality without user interaction. The provided sources do not show confirmed active exploitation.

Executive priority

Treat as high priority for cryptographic and Java platform owners, especially where BC-JAVA is used in exposed services. Patch through normal emergency or accelerated security update channels; active exploitation is not evidenced in the supplied sources.

Technical view

CVE-2026-5598 is a covert timing channel in BC-JAVA core FrodoEngine.Java. Non-constant time comparisons in FrodoKEM affect BC-JAVA 1.71 before 1.80.2, 1.81 before 1.81.1, and 1.82 before 1.84. CVSS v4.0 score is 8.9, CWE-385.

Likely exposure

Exposure is most likely in Java applications or platforms bundling vulnerable BC-JAVA core versions and using FrodoKEM or related post-quantum cryptographic paths. Systems not using affected versions or FrodoKEM are less likely exposed, but dependency inventory is required.

Exploitation context

The bundle marks CISA KEV as false and provides no cited evidence of exploitation in the wild. The risk is a timing side channel that could disclose private key material under observable conditions; exact practical exploitability is not established in the supplied evidence.

Researcher notes

Focus review on BC-JAVA FrodoEngine.Java changes in the cited patch commits and version boundaries. Avoid assuming broader Bouncy Castle impact beyond BC-JAVA core modules and the affected ranges named in the CVE bundle.

Mitigation direction

  • Upgrade BC-JAVA to 1.80.2, 1.81.1, 1.84, or later as applicable.
  • Apply relevant Red Hat security errata for vendor-managed packages.
  • Prioritize internet-facing or multi-tenant services using BC-JAVA cryptographic operations.
  • Check vendor guidance before adding compensating controls not named in advisories.
  • Evaluate key replacement if FrodoKEM private keys faced untrusted timing observation.

Validation and detection

  • Inventory SBOMs and dependency manifests for BC-JAVA core versions.
  • Confirm no runtime classpath includes affected BC-JAVA releases.
  • Identify applications using FrodoKEM or post-quantum KEM functionality.
  • Verify patched versions are deployed in build and production images.
  • Track Red Hat advisory applicability for managed Linux packages.
Prepared
Confidence
high
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-385: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2026-5598 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.9 (4.0)
Known Exploited
No
Published

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:U/S:P/AU:Y/U:Red

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
12Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.9CVSS 4.0HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:U/S:P/AU:Y/U:Red——bcorg
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 4.0 score

8.9High
CVSS 4.0 vector shape for CVE-2026-5598Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:U/S:P/AU:Y/U:Red

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPbouncycastle: BC-JAVA: private key leakage via non-constant time comparisons
other:Red Hat severity ratingcvssV3_1
  • 2026-04-15T10:01:04.531Z: Reported to Red Hat.
  • 2026-04-15T09:05:56.277Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Legion of the Bouncy Castle Inc.BC-JAVAcore, 1.71, 1.81, 1.82unaffected
Weakness

CWE details

CWE-385

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-385 · source CWE mapping

Covert Timing Channel

Covert Timing Channel represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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