CVE-2026-12852: In Bouncy Castle for Java before 1.85, MLS wire decoder allocates attacker-declared opaque length before bound

Q: How do I fix CVE-2026-12852?

bc-java: upgrade to 1.85. Exact commands for each OS are on this page.

Q: Is CVE-2026-12852 being exploited?

CVE-2026-12852 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-12852 affect?

CVE-2026-12852 affects bc-java. Severity is high (CVSS 7.5). In Bouncy Castle for Java before 1.85, MLS wire decoder allocates attacker-declared opaque length before bounds check.

Q: How urgent is CVE-2026-12852?

Priority 37/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-12852 is a high-severity flaw (CVSS 7.5) affecting bc-java. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Bouncy Castle for Java before 1.85, MLS wire decoder allocates attacker-declared opaque length before bounds check.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 77%)
CISA exploited list	No
Weakness	CWE-789
Published	2026-08-03
Last modified	2026-10-23

Publisher (CNA): bcorg · Vendor: bouncycastle

Am I affected?

Timeline

2026-08-03 04:16 UTCPublished CVE record published
2026-10-23 22:10 UTCUpdated Record last modified

bouncycastle bc-java UPGRADE

Affected: < 1.85

Fixed in: 1.85

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy bc-java || rpm -q bc-java || bc-java --version

2. UPGRADE to 1.85 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bc-java

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bc-java

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-12852?

bc-java: upgrade to 1.85. Exact commands for each OS are on this page.

Is CVE-2026-12852 being exploited?

CVE-2026-12852 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-12852 affect?

CVE-2026-12852 affects bc-java. Severity is high (CVSS 7.5). In Bouncy Castle for Java before 1.85, MLS wire decoder allocates attacker-declared opaque length before bounds check.

How urgent is CVE-2026-12852?

Priority 37/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-59644 HIGH 7.5 UPGRADE In Bouncy Castle for Java before 1.85, MLS hash-ratchet honours arbitrary 32-bit generation counter from sende
CVE-2026-59652 MEDIUM 6.5 UPGRADE In Bouncy Castle for Java before 1.85, LDAP filter injection in legacy jdk1.4 LDAPStoreHelper.

References

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