CVE-2026-12817: In Bouncy Castle for Java before 1.85, OpenPGP AEAD decryption skips final tag on chunk-aligned data

Q: How do I fix CVE-2026-12817?

bc-java: upgrade to 1.85; bcpg-fips: upgrade to 1.0.13, 2.0.13, 2.1.13; bouncy castle for java lts: upgrade to newer than 2.73.11. Exact commands for each OS are on this page.

Q: Is CVE-2026-12817 being exploited?

CVE-2026-12817 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-2026-12817 affect?

CVE-2026-12817 affects bc-java, bcpg-fips, bouncy castle for java lts. Severity is high (CVSS 8.6). In Bouncy Castle for Java before 1.85, OpenPGP AEAD decryption skips final tag on chunk-aligned data. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpg-fips 1.0.13 (1.0.X

Q: How urgent is CVE-2026-12817?

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

Routine

HIGH 8.6REMOTEUPGRADEUPGRADEUPGRADE

CVE-2026-12817 is a high-severity flaw (CVSS 8.6) affecting bc-java, bcpg-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, OpenPGP AEAD decryption skips final tag on chunk-aligned data. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpg-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (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	8.6 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 94%)
CISA exploited list	No
Weakness	CWE-354
Published	2026-08-03
Last modified	2026-08-31

Publisher (CNA): bcorg · Vendor: bouncycastle

Last updated 2026-08-31 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-03 04:16 UTCPublished CVE record published
2026-08-31 15:16 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 bcpg-fips UPGRADE

Affected: >= 1.0.7 and < 1.0.13 · >= 2.0.8 and < 2.0.13 · >= 2.1.10 and < 2.1.13

Fixed in: 1.0.13, 2.0.13, 2.1.13

Safe to downgrade to: a release before 1.0.7

1. Check installed version

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

2. UPGRADE to 1.0.13 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bcpg-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 1.0.7 (Debian / Ubuntu)

apt-cache madison bcpg-fips sudo apt install bcpg-fips=<VERSION_BEFORE_1.0.7> sudo apt-mark hold bcpg-fips

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

dnf --showduplicates list bcpg-fips sudo dnf downgrade bcpg-fips-<VERSION_BEFORE_1.0.7> sudo dnf versionlock add bcpg-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-2026-12817?

bc-java: upgrade to 1.85; bcpg-fips: upgrade to 1.0.13, 2.0.13, 2.1.13; bouncy castle for java lts: upgrade to newer than 2.73.11. Exact commands for each OS are on this page.

Is CVE-2026-12817 being exploited?

CVE-2026-12817 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-2026-12817 affect?

CVE-2026-12817 affects bc-java, bcpg-fips, bouncy castle for java lts. Severity is high (CVSS 8.6). In Bouncy Castle for Java before 1.85, OpenPGP AEAD decryption skips final tag on chunk-aligned data. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpg-fips 1.0.13 (1.0.X

How urgent is CVE-2026-12817?

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

Software pages

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References

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