CVE-2018-8753: The IKEv1 implementation in Clavister cOS Core before 11.00.11, 11.20.xx before 11.20.06, and 12.00.xx before

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MEDIUM 5.9REMOTEUPGRADE

CVE-2018-8753 is a medium-severity flaw (CVSS 5.9) affecting cos core. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The IKEv1 implementation in Clavister cOS Core before 11.00.11, 11.20.xx before 11.20.06, and 12.00.xx before 12.00.09 allows remote attackers to decrypt RSA-encrypted nonces by leveraging a Bleichenbacher attack.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	1.6% (top 24%)
CISA exploited list	No
Published	2018-08-15
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: clavister

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-08-15 18:29 UTCPublished CVE record published
2026-06-17 02:05 UTCUpdated Record last modified

clavister cos core UPGRADE

Affected: < 11.00.11 · >= 11.20.00 and < 11.20.06 · >= 12.00.00 and < 12.00.09

Fixed in: 11.00.11, 11.20.06, 12.00.09

Safe to downgrade to: a release before 11.20.00

1. Check installed version

apt-cache policy cos-core || rpm -q cos-core || cos-core --version

2. UPGRADE to 11.00.11 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cos-core

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cos-core

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 11.20.00 (Debian / Ubuntu)

apt-cache madison cos-core sudo apt install cos-core=<VERSION_BEFORE_11.20.00> sudo apt-mark hold cos-core

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

dnf --showduplicates list cos-core sudo dnf downgrade cos-core-<VERSION_BEFORE_11.20.00> sudo dnf versionlock add cos-core

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-2018-8753?

cos core: upgrade to 11.00.11, 11.20.06, 12.00.09. Exact commands for each OS are on this page.

Is CVE-2018-8753 being exploited?

CVE-2018-8753 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-2018-8753 affect?

CVE-2018-8753 affects cos core. Severity is medium (CVSS 5.9). The IKEv1 implementation in Clavister cOS Core before 11.00.11, 11.20.xx before 11.20.06, and 12.00.xx before 12.00.09 allows remote attackers to decrypt RSA-encrypted nonces by leveraging a Bleichenbacher attack.

How urgent is CVE-2018-8753?

Priority 45/100. Remotely exploitable, no login, no user action

References

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