How severe is CVE-2026-59646?

CVE-2026-59646 has a CVSS 4.0 base score of 8.7, rated high severity.

Is CVE-2026-59646 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-59646?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-59646 published?

CVE-2026-59646 was published on 2026-08-03 and last updated on 2026-08-04.

CVE-2026-59646

CVE-2026-59646 is a high-severity vulnerability with a CVSS 4.0 base score of 8.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-789.

Key facts

Severity: High (CVSS 4.0 base score 8.7)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-789
Published: 2026-08-03
Last modified: 2026-08-04

Description

In Bouncy Castle for Java before 1.85, DTLS handshake reassembler allocates buffer from unchecked 24-bit length. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).

Frequently asked questions

What is CVE-2026-59646?: In Bouncy Castle for Java before 1.85, DTLS handshake reassembler allocates buffer from unchecked 24-bit length. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).
How severe is CVE-2026-59646?: CVE-2026-59646 has a CVSS 4.0 base score of 8.7, rated high severity.
Is CVE-2026-59646 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-59646?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-59646 published?: CVE-2026-59646 was published on 2026-08-03 and last updated on 2026-08-04.

References

Other CWE-789 vulnerabilities

CVE-2021-34869 — High (CVSS 8.8): This vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop…
CVE-2021-34868 — High (CVSS 8.8): This vulnerability allows local attackers to escalate privileges on affected installations of Parallels Desktop…
CVE-2026-69219 — High (CVSS 8.7): The RabbitMQ Java client library allows Java and JVM-based applications to connect to and interact with RabbitMQ nodes.…
CVE-2026-58067 — High (CVSS 8.7): A vulnerability in Veeam Service Provider Console allowing an unauthenticated attacker to exhaust host memory and cause…
CVE-2026-14682 — High (CVSS 8.7): In Bouncy Castle for Java before 1.85, Possible OOM from unbounded up-front allocation on a definite-length read. This…
CVE-2026-12852 — High (CVSS 8.7): In Bouncy Castle for Java before 1.85, MLS wire decoder allocates attacker-declared opaque length before bounds check.

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