CVE-2026-5588: PKIX draft CompositeVerifier accepts empty signature sequence as valid.
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.8%
Up from 0.7% on .
EPSS score, percentile 55.7 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 6.3 Medium
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
- Which versions are affected?
Affected
- from 1.67 to before 1.80.2
- from 1.81 to before 1.81.1
- from 1.82 to before 1.84
- from 2.0.6 to before 2.0.11
- from 2.1.7 to before 2.1.11
- from 2.73.7 to before 2.73.11
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Advisories and patches
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 1.67 to before 1.80.2 |
| Affected | from 1.81 to before 1.81.1 |
| Affected | from 1.82 to before 1.84 |
Versions not listed are: unaffected.
| Status | Versions |
|---|---|
| Affected | from 2.0.6 to before 2.0.11 |
| Affected | from 2.1.7 to before 2.1.11 |
Versions not listed are: unaffected.
| Status | Versions |
|---|---|
| Affected | from 2.73.7 to before 2.73.11 |
Versions not listed are: unaffected.
Source: CVE List, as of . About the data.
About this vulnerability
Use of a Broken or Risky Cryptographic Algorithm vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA bcpkix on all (pkix modules), Legion of the Bouncy Castle Inc. BCPKIX-FIPS bcpkix on All (pkix modules), Legion of the Bouncy Castle Inc. BCPIX-LTS bcpkix on All (pkix modules). This vulnerability is associated with program files JcaContentVerifierProviderBuilder.Java, JcaContentVerfierPro…
Summary: CVE record, as of .
- CISA has not added CVE-2026-5588 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 15 Apr 2026.
- The CVE record carries a CVSS v4.0 base score of 6.3 (Medium), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.8% (percentile 55.7), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact partial.
- The credits in the CVE record name Anthropic (Claude) as finder.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
PKIX draft CompositeVerifier accepts empty signature sequence as valid.
Use of a Broken or Risky Cryptographic Algorithm vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA bcpkix on all (pkix modules), Legion of the Bouncy Castle Inc. BCPKIX-FIPS bcpkix on All (pkix modules), Legion of the Bouncy Castle Inc. BCPIX-LTS bcpkix on All (pkix modules). This vulnerability is associated with program files JcaContentVerifierProviderBuilder.Java, JcaContentVerfierProviderBuilder.Java. This issue affects BC-JAVA: from 1.67 before 1.80.2, from 1.81 before 1.81.1, from 1.82 before 1.84; BCPKIX-FIPS: from 2.0.6 before 2.0.11, from 2.1.7 before 2.1.11; BCPIX-LTS: from 2.73.7 before 2.73.11.
Source: CVE List, as of . About the data.
Weakness
CWE-327
- CWE-327: Use of a Broken or Risky Cryptographic Algorithm
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |