CVE-2026-59639: In Bouncy Castle for Java before 1.85, CMS verifySignatures returns true for SignedData with zero signers

Q: How do I fix CVE-2026-59639?

bc-java: upgrade to 1.85; bcpkix-fips: upgrade to 1.0.12, 2.0.12, 2.1.12; bouncy castle for java lts: upgrade to newer than 2.73.11. Exact commands for each OS are on this page.

Q: Is CVE-2026-59639 being exploited?

CVE-2026-59639 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-2026-59639 affect?

CVE-2026-59639 affects bc-java, bcpkix-fips, bouncy castle for java lts. Severity is high (CVSS 7.5). In Bouncy Castle for Java before 1.85, CMS verifySignatures returns true for SignedData with zero signers. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.12

Q: How urgent is CVE-2026-59639?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.5REMOTEUPGRADEUPGRADEUPGRADE

CVE-2026-59639 is a high-severity flaw (CVSS 7.5) affecting bc-java, bcpkix-fips, bouncy castle for java lts. 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, CMS verifySignatures returns true for SignedData with zero signers. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.12 (1.0.X series), 2.0.12 (2.0.X series) and 2.1.12 (2.1.X series).

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	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-347
Published	2026-08-03
Last modified	2026-08-28

Publisher (CNA): bcorg · Vendor: bouncycastle

Last updated 2026-08-28 · 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
2026-08-28 15:33 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 bcpkix-fips UPGRADE

Affected: < 1.0.12 · >= 2.0.7 and < 2.0.12 · >= 2.1.8 and < 2.1.12

Fixed in: 1.0.12, 2.0.12, 2.1.12

Safe to downgrade to: a release before 2.0.7

1. Check installed version

apt-cache policy bcpkix-fips || rpm -q bcpkix-fips || bcpkix-fips --version

2. UPGRADE to 1.0.12 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade bcpkix-fips

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bcpkix-fips

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 2.0.7 (Debian / Ubuntu)

apt-cache madison bcpkix-fips sudo apt install bcpkix-fips=<VERSION_BEFORE_2.0.7> sudo apt-mark hold bcpkix-fips

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

dnf --showduplicates list bcpkix-fips sudo dnf downgrade bcpkix-fips-<VERSION_BEFORE_2.0.7> sudo dnf versionlock add bcpkix-fips

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.

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.

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-2026-59639?

bc-java: upgrade to 1.85; bcpkix-fips: upgrade to 1.0.12, 2.0.12, 2.1.12; bouncy castle for java lts: upgrade to newer than 2.73.11. Exact commands for each OS are on this page.

Is CVE-2026-59639 being exploited?

CVE-2026-59639 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-2026-59639 affect?

CVE-2026-59639 affects bc-java, bcpkix-fips, bouncy castle for java lts. Severity is high (CVSS 7.5). In Bouncy Castle for Java before 1.85, CMS verifySignatures returns true for SignedData with zero signers. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.12

How urgent is CVE-2026-59639?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Software pages

Java vulnerabilities

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References

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