How severe is CVE-2026-59644?

CVE-2026-59644 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-59644 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (40th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-59644?

CVE-2026-59644 affects Bouncycastle Bc-java. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-59644?

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-2026-59644 published?

CVE-2026-59644 was published on 2026-08-03 and last updated on 2026-08-31.

CVE-2026-59644

CVE-2026-59644 is a high-severity vulnerability in Bouncycastle Bc-java with a CVSS 3.x base score of 7.5. 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-834.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.7
EPSS exploit prediction: 0% (40th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-834
Affected product: Bouncycastle Bc-java
Published: 2026-08-03
Last modified: 2026-08-31

Description

In Bouncy Castle for Java before 1.85, MLS hash-ratchet honours arbitrary 32-bit generation counter from sender.

Frequently asked questions

What is CVE-2026-59644?: In Bouncy Castle for Java before 1.85, MLS hash-ratchet honours arbitrary 32-bit generation counter from sender.
How severe is CVE-2026-59644?: CVE-2026-59644 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-59644 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (40th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-59644?: CVE-2026-59644 affects Bouncycastle Bc-java. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-59644?: 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-2026-59644 published?: CVE-2026-59644 was published on 2026-08-03 and last updated on 2026-08-31.

References

Affected products (1)

cpe:2.3:a:bouncycastle:bc-java:*:*:*:*:*:*:*:*

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