CVE-2026-8763: In Bouncy Castle for Java before 1.85, Name Constraints bypass via trailing dot in rfc822Name and URI

This month

CRITICAL 9.1REMOTEUPGRADEUPGRADEUPGRADE

CVE-2026-8763 is a critical-severity flaw (CVSS 9.1) affecting bc-java, bouncy castle for java lts, fips java api. 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, Name Constraints bypass via trailing dot in rfc822Name and URI. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 1.0.2.7 (1.0.X series), 2.0.2 (2.0.X series) and 2.1.3 (2.1.X series).

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 63%)
CISA exploited list	No
Weakness	CWE-295
Published	2026-08-03
Last modified	2026-09-02

Publisher (CNA): bcorg · Vendor: bouncycastle

Last updated 2026-09-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-03 01:16 UTCPublished CVE record published
2026-09-02 14:28 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.

bouncycastle bouncy castle for java lts UPGRADE

Affected: <= 2.73.11

Fixed in: newer than 2.73.11

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy bouncy-castle-for-java-lts || rpm -q bouncy-castle-for-java-lts || bouncy-castle-for-java-lts --version

2. UPGRADE to newer than 2.73.11 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bouncy-castle-for-java-lts

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bouncy-castle-for-java-lts

Note

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

bouncycastle fips java api UPGRADE

Affected: >= 1.0.0 and < 1.0.2.7 · >= 2.0.0 and < 2.0.2 · >= 2.1.0 and < 2.1.3

Fixed in: 1.0.2.7, 2.0.2, 2.1.3

Safe to downgrade to: a release before 1.0.0

1. Check installed version

apt-cache policy fips-java-api || rpm -q fips-java-api || fips-java-api --version

2. UPGRADE to 1.0.2.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade fips-java-api

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fips-java-api

Note

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

3. If no update is available yet, DOWNGRADE to a release before 1.0.0 (Debian / Ubuntu)

apt-cache madison fips-java-api sudo apt install fips-java-api=<VERSION_BEFORE_1.0.0> sudo apt-mark hold fips-java-api

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list fips-java-api sudo dnf downgrade fips-java-api-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add fips-java-api

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2026-8763?

bc-java: upgrade to 1.85; bouncy castle for java lts: upgrade to newer than 2.73.11; fips java api: upgrade to 1.0.2.7, 2.0.2, 2.1.3. Exact commands for each OS are on this page.

Is CVE-2026-8763 being exploited?

CVE-2026-8763 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-2026-8763 affect?

CVE-2026-8763 affects bc-java, bouncy castle for java lts, fips java api. Severity is critical (CVSS 9.1). In Bouncy Castle for Java before 1.85, Name Constraints bypass via trailing dot in rfc822Name and URI. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 1.0.2.7 (1.0.X

How urgent is CVE-2026-8763?

Priority 46/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Java vulnerabilities

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References

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