CVE.org (no NVD analysis yet)· CNA bcorg

CVE-2026-71889: PKIXCertPathReviewer does not apply X.509 name constraints to the target certificate

Noroxi assessment

Priority: Monitor (action score 34/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.16% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: Legion of the Bouncy Castle Inc. BC-FJA 1.0.13, 2.0.13, 2.1.13; Legion of the Bouncy Castle Inc. BC-JAVA 1.86; Legion of the Bouncy Castle Inc. BC-LTS-JAVA 2.73.13.

Low priority for now. Upgrade to Legion of the Bouncy Castle Inc. BC-FJA 1.0.13, 2.0.13, 2.1.13; Legion of the Bouncy Castle Inc. BC-JAVA 1.86; Legion of the Bouncy Castle Inc. BC-LTS-JAVA 2.73.13 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In Bouncy Castle for Java before 1.86, neither copy of PKIXCertPathReviewer - org.bouncycastle.pkix.jcajce.PKIXCertPathReviewer nor the legacy org.bouncycastle.x509.PKIXCertPathReviewer - applied X.509 name constraints to the end-entity certificate. checkNameConstraints walked the path with a loop bound of index greater than zero, which is the bound the CA-only steps require, but index zero is the target certificate under the standard CertPath ordering, so the permitted and excluded subtree checks of RFC 5280 sec. 6.1.3 (b) and (c) never ran against the leaf's subject DN or its subjectAltName. A chain whose leaf violated a NameConstraints extension imposed by its own issuing CA therefore reported isValidCertPath() true with an empty error list, while CertPathValidator.getInstance("PKIX", "BC"), which shares no code with the reviewer, rejected the identical chain against the identical trust anchor. An application using the reviewer to make the trust decision rather than for diagnostics alongside a real validation accepted a certificate the constrained CA was never authorised to issue. Both copies now check every certificate in the path including the target, waive the sec. 4.2.1.10 self-issued exemption for the final certificate as sec. 6.1.3 requires, and skip the sec. 6.1.4 (g) constraint-accumulation step for the target. This issue also affects Bouncy Castle for Java LTS before 2.73.13, which carries only the org.bouncycastle.pkix.jcajce copy of the reviewer. It also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).

HighCVSS 8.7 · v4.0—No exploit Fix available

Published: Oct 3, 2026
Updated: Oct 6, 2026
EPSS: 0.1% · 5th percentile
CWE: CWE-295

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 34 / 40 · 8.7 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.1%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · bcorg: 8.7; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

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—

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This vulnerability is about certificate validation or weak cryptography. The free SSL checker tests your certificate, enabled TLS versions and weak ciphers.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (bcorg). Independent of NVD's CPE analysis and usually ahead of it.

Legion of the Bouncy Castle Inc. BC-FJA
- 1.0.4 and later · before 1.0.13affected · maven
- 2.0.0 and later · before 2.0.13affected · maven
- 2.1.0 and later · before 2.1.13affected · maven
Legion of the Bouncy Castle Inc. BC-JAVA
- before 1.86affected · maven
- before 1.86affected · maven
Legion of the Bouncy Castle Inc. BC-LTS-JAVA
- 2.73.0 and later · before 2.73.13affected · maven

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	bouncycastle	from 0	—
Debian:14	bouncycastle	before 1.86-1	1.86-1
openSUSE:Tumbleweed	bouncycastle	before 1.86-1.1	1.86-1.1
SUSE:Linux Enterprise Module for Development Tools 15 SP7	bouncycastle	before 1.86-150200.3.41.1	1.86-150200.3.41.1

Same product

legion of the bouncy castle inc.: all records

Other highest-scoring records for the same primary product.

CVE-2025-14813GOSTCTR implementation unable to process more than 255 blocks correctly
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CVE-2026-71885MLS X.509 credential not bound to the LeafNode signature key
36Monitor
CVE-2026-5598Non-constant time comparisons risk private key leakage in FrodoKEM.
35Monitor

Published before and after this one in the same product

← EarlierCVE-2026-71887Oct 3, 2026 · OpenPGP data signature accepted from a signing subkey without cross-certification
32Monitor
← EarlierCVE-2026-71888Oct 3, 2026 · CMS AuthenticatedData exposes attacker-inserted authAttrs when digestAlgorithm is absent
34Monitor
Later →CVE-2026-71890Oct 3, 2026 · MLS external commit can remove an arbitrary group member
34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Legion of the Bouncy Castle Inc. BC-FJA	1.0.13	Vendor (CNA)
Legion of the Bouncy Castle Inc. BC-FJA	2.0.13	Vendor (CNA)
Legion of the Bouncy Castle Inc. BC-FJA	2.1.13	Vendor (CNA)
Legion of the Bouncy Castle Inc. BC-JAVA	1.86	Vendor (CNA)
Legion of the Bouncy Castle Inc. BC-LTS-JAVA	2.73.13	Vendor (CNA)
debian:bouncycastle	1.86-1 · Debian:14	Package registry (OSV)
opensuse:bouncycastle	1.86-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
suse:bouncycastle	1.86-150200.3.41.1 · SUSE:Linux Enterprise Module for Development Tools 15 SP7	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

PublishedOct 3, 2026
Fix recordedOct 3, 2026same day
TodayOct 25, 2026+22 d

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

bcgit/bc-javacommit 06dcff2

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Yu Bao from the PayPal Cyber Security Teamreporter

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-295 · Improper Certificate Validation

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber

nvd-secondary

Root cause

A certificate validation error is silently swallowed instead of terminating the connection. Often, code added for a test environment makes its way into production.

The bug in code

The whole CWE-295 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

kotlin

1override fun checkServerTrusted(chain: Array<X509Certificate>, type: String) {
2  // Left empty for the test environment
3}

Fixed

kotlin

1val client = OkHttpClient.Builder()
2  .certificatePinner(
3    CertificatePinner.Builder()
4      .add("api.sirius.example", "sha256/…")
5      .build()
6  ).build()

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

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Change log

SSVC exploitation— → noneOct 5, 2026, 6:07 PM UTC
Exploit maturity— → noneOct 3, 2026, 10:07 AM UTC
Fix✗ → ✓Oct 3, 2026, 10:07 AM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/bcgit/bc-java/commit/06dcff2f51037095de126986285c998e3455ab85

Show all references (1 more)

github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9071889

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

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