dbcve.org
Debian LinuxOperating system · Debian

CVE-2021-45079

CRITICAL · 9.1 CVSS v3.1 Published 2022-01-31
Fix available
A fix is available. Upgrade to 5.9.5 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In strongSwan before 5.9.5, a malicious responder can send an EAP-Success message too early without actually authenticating the client and (in the case of EAP methods with mutual authentication and EAP-only authentication for IKEv2) even without server authentication.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In strongSwan before 5.9.5, the IKEv2 daemon incorrectly handles EAP authentication, allowing a malicious responder to send an EAP-Success message prematurely without completing client authentication. In configurations using EAP methods with mutual authentication or EAP-only authentication for IKEv2, the attacker can also bypass server authentication entirely, effectively enabling an unauthenticated man-in-the-middle attack.

MitigationUpgrade strongSwan to version 5.9.5 or later. If immediate upgrade is not feasible, restrict IKEv2 peer connections to trusted endpoints and implement additional network-level controls to prevent unauthorized responders.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 9.0= 10.0= 11.0
FedoraOperating system
Affected:= 34= 35
Ubuntu LinuxOperating system
Affected:= 14.04= 16.04= 18.04= 20.04= 21.10
StrongswanApplication
Affected:>= 4.1.2, < 5.9.5
Extra Packages For Enterprise LinuxApplication
Affected:= 7.0= 8.0= 9.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if strongSwan is installed
    Run `which charon` or `which ipsec`, or query your package manager (dpkg -l | grep strongswan or rpm -qa | grep strongswan)
    Affected if strongSwan is not installed on the system
  2. Determine the installed strongSwan version
    Run `ipsec version` or query the package database (dpkg -l strongswan* or rpm -qa strongswan*)
    Affected if The installed version is 5.9.5 or lower, specifically any version >= 4.1.2 and < 5.9.5
  3. Verify IKEv2 is configured
    Examine /etc/ipsec.conf and look for 'keyexchange=ikev2' or IKEv2-related connection definitions
    Affected if The system is configured to accept IKEv2 connections
  4. Confirm EAP authentication is enabled
    Check /etc/ipsec.secrets for 'EAP-' lines or examine the ipsec.conf for 'leftauth=eap' or 'rightauth=eap' settings in IKEv2 connections
    Affected if EAP authentication methods are configured for IKEv2 (particularly EAP-only or EAP mutual authentication)

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.9.5 or later
Fixed in 5.9.5
Interim mitigation

Upgrade strongSwan to version 5.9.5 or later. If immediate upgrade is not feasible, restrict IKEv2 peer connections to trusted endpoints and implement additional network-level controls to prevent unauthorized responders.

Recommended fix High confidence

strongSwan 5.9.5 or later

  1. 1. Identify current strongSwan version installed (e.g., run `ipsec --version` or use package manager like `dpkg -l | grep strongswan` on Debian/Ubuntu, `rpm -qa | grep strongswan` on RHEL/Fedora)
  2. 2. Update the strongSwan package to version 5.9.5 or later using your distribution's package manager (e.g., `apt-get update && apt-get install strongswan` on Debian/Ubuntu, `dnf update strongswan` on Fedora/RHEL)
  3. 3. After installation, verify the new version is installed correctly with `ipsec --version`
  4. 4. Restart the ipsec service to apply the update (e.g., `systemctl restart strongswan` or `systemctl restart ipsec`)
  5. 5. Verify the service is running correctly and test VPN connectivity

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,072.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-45079 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-45079 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data