VulnerabilityPublished 3 Aug 2026

CVE-2026-58062: Legion of the Bouncy Castle BC-JAVA · Improper Certificate Validation

Affects Legion of the Bouncy Castle BC-JAVASource CVE Database V5

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Not known to be exploited · CVSS 9.3 Critical : upgrade to 1.85 as a priority.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 4.0 base score

9.3Critical

How severe the flaw is on the 0–10 CVSS scale.

EPSS

0.3% chance of exploitation in 30 days – higher than 30% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Total control over the software or total information disclosure

CISA SSVC assessment, 2026-08-03.

Patch

Available – fixed in 1.85, 2.73.12, 2.1.3 +1

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

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Supplemental metrics

Provider Urgency: Amber

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Provider Urgency: Amber: Provider has assessed the impact of this vulnerability as having a moderate urgency.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 3 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
Public exploit code: GitHub proofs of concept
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), GitHub proofs of concept, the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade BC-JAVA and Legion of the Bouncy Castle Inc./bcprov to 1.85; BC-LTS-JAVA and Legion of the Bouncy Castle Inc./bcprov-lts8on to 2.73.12; BC-FJA and Legion of the Bouncy Castle Inc./bc-fips to 2.1.3 or 2.0.2.

Affected software

Product	Affected	Fixed in
Legion of the Bouncy Castle Inc.BC-JAVA	Affected >=1.66 <1.85	Fixed in 1.85
Legion of the Bouncy Castle Inc.BC-LTS-JAVA	Affected >=2.73.0 <2.73.12	Fixed in 2.73.12
Legion of the Bouncy Castle Inc.BC-FJA	Affected >=2.1.0 <2.1.3	Fixed in 2.1.3
Legion of the Bouncy Castle Inc.BC-FJA	Affected >=2.0.0 <2.0.2	Fixed in 2.0.2
MavenLegion of the Bouncy Castle Inc./bcprov`pkg:maven/Legion of the Bouncy Castle Inc./bcprov`Other threats	Affected >=1.66 <1.85	Fixed in 1.85
MavenLegion of the Bouncy Castle Inc./bcprov-lts8on`pkg:maven/Legion of the Bouncy Castle Inc./bcprov-lts8on`Other threats	Affected >=2.73.0 <2.73.12	Fixed in 2.73.12

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Fixed versions are available and should be applied to remediate this vulnerability. Upgrade to BC-JAVA version 1.85 or later, LTS version 2.73.12 or later, or FIPS versions 2.0.2 or 2.1.3 or later as appropriate. No other mitigation is indicated by the vendor advisory.

Description

CVE-2026-58062 is a critical vulnerability in Legion of the Bouncy Castle Inc.'s BC-JAVA library involving improper certificate validation. Specifically, in versions before 1.85 (and corresponding LTS and FIPS versions), the library accepts stapled OCSP responses without properly binding them to the certificate being checked. This flaw affects multiple branches of BC-JAVA and has been fixed in versions 1.85, 2.73.12, 2.0.2, and 2.1.3.

Impact

This vulnerability allows an attacker to bypass certificate validation by exploiting the acceptance of stapled OCSP responses that are not properly bound to the certificate being checked. This can lead to acceptance of revoked or fraudulent certificates, potentially enabling man-in-the-middle attacks or other forms of impersonation in TLS communications that rely on BC-JAVA for certificate validation.

Summary

The vulnerability CVE-2026-58062 in Bouncy Castle for Java (BC-JAVA) concerns improper certificate validation due to acceptance of stapled OCSP responses that are not bound to the certificate under validation. This affects versions prior to 1.85 in the mainline, prior to 2.73.12 in the LTS branch, and prior to 2.0.2 and 2.1.3 in the FIPS branches. The flaw could allow an attacker to bypass certificate validation checks, undermining the security guarantees of TLS connections that rely on OCSP stapling for revocation status. The issue is tracked under CWE-295 (Improper Certificate Validation) and has a high CVSS 4.0 score of 9.3, indicating critical severity. Fixed versions are 1.85, 2.73.12, 2.0.2, and 2.1.3.

CWE-295Improper Certificate Validation (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not validate, or incorrectly validates, a certificate.
Architecture and Design · Implementation
Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
Implementation
If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
OWASP Cheat Sheets
Transport Layer Protection (opens in a new tab)
TLS Cipher String (opens in a new tab)
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V9.2.1 (opens in a new tab)
V1.9.2 (opens in a new tab)
V2.8.5 (opens in a new tab)
Attack patterns
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2026, 01:44 UTC

Public exploits and detectionGitHub proofs of concept

WeaknessesCWE-295

Technical details

References

Community reviews

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