CVE-2021-45079
published 2022-01-31CVE-2021-45079: 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…
PriorityP262critical9.1CVSS 3.1
AVNACLPRNUINSUCHINAH
EPSS
2.78%
86.3th percentile
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.
Affected
25 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| canonical | ubuntu_linux | — | — |
| canonical | ubuntu_linux | — | — |
| canonical | ubuntu_linux | — | — |
| canonical | ubuntu_linux | — | — |
| canonical | ubuntu_linux | — | — |
| debian | debian_linux | — | — |
| debian | debian_linux | — | — |
| debian | debian_linux | — | — |
| debian | strongswan | < strongswan 5.9.5-1 (bookworm) | strongswan 5.9.5-1 (bookworm) |
| fedoraproject | extra_packages_for_enterprise_linux | — | — |
| fedoraproject | extra_packages_for_enterprise_linux | — | — |
| fedoraproject | extra_packages_for_enterprise_linux | — | — |
| fedoraproject | fedora | — | — |
| fedoraproject | fedora | — | — |
| msrc | cbl2_strongswan_5.9.5-1_on_cbl_mariner_2.0 | — | — |
| msrc | cbl_mariner_1.0_arm | — | — |
| msrc | cbl_mariner_1.0_x64 | — | — |
| msrc | cbl_mariner_2.0_arm | — | — |
| msrc | cbl_mariner_2.0_x64 | — | — |
| msrc | cm1_strongswan_5.7.2-5_on_cbl_mariner_1.0 | — | — |
| strongswan | strongswan | >= 0 < 5.9.1-1+deb11u2 | 5.9.1-1+deb11u2 |
| strongswan | strongswan | >= 0 < 5.9.5-1 | 5.9.5-1 |
| strongswan | strongswan | >= 0 < 5.9.5-1 | 5.9.5-1 |
| strongswan | strongswan | >= 0 < 5.9.5-1 | 5.9.5-1 |
| strongswan | strongswan | >= 4.1.2 < 5.9.5 | 5.9.5 |
Detection & IOCsextracted from sources · hover to see the quote
- →A malicious IKEv2 responder sends an EAP-Success message prematurely (before completing actual client authentication), which can be detected by monitoring for EAP-Success messages arriving out of the expected EAP exchange sequence in IKEv2 traffic. ↗
- →The vulnerability affects strongSwan versions before 5.9.5; detection should focus on identifying unpatched strongSwan instances (prior to 5.9.5) acting as IKEv2 initiators that may accept premature EAP-Success messages. ↗
- →Exploitation can result in a crash (denial of service) or authentication bypass; monitor strongSwan daemon logs for unexpected EAP-Success handling, crashes, or successful IKEv2 session establishment without completed mutual authentication. ↗
- ·The authentication bypass is specifically exploitable when EAP methods with mutual authentication are used, or when EAP-only authentication for IKEv2 is configured; deployments not using these EAP modes have reduced exposure. ↗
- ·Fixed versions are strongSwan 5.9.5 (upstream) and Debian-specific backports (5.9.1-1+deb11u2 for bullseye); ensure the running strongSwan version meets or exceeds these thresholds. ↗
CVSS provenance
nvdv3.19.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
nvdv2.05.8MEDIUMAV:N/AC:M/Au:N/C:P/I:N/A:P
osv9.1CRITICAL
vendor_debian9.1CRITICAL
vendor_msrc9.1CRITICAL
Stop checking back — get the weekly exploitation signal.
Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.
GHSA
GHSA-8x8f-8g3r-h75g: In strongSwan before 5
ghsa_unreviewed·2022-02-08
CVE-2021-45079 [CRITICAL] CWE-287 GHSA-8x8f-8g3r-h75g: In strongSwan before 5
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.
OSV
CVE-2021-45079: In strongSwan before 5
osv·2022-01-31·CVSS 9.1
CVE-2021-45079 [CRITICAL] CVE-2021-45079: In strongSwan before 5
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.
Ubuntu
strongSwan vulnerability
vendor_ubuntu·2022-01-24
CVE-2021-45079 strongSwan vulnerability
Title: strongSwan vulnerability
Summary: strongSwan could crash or allow unintended access to network services.
USN-5250-1 fixed a vulnerability in strongSwan. This update provides
the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.
Original advisory details:
Zhuowei Zhang discovered that stringSwan incorrectly handled EAP
authentication. A remote attacker could use this issue to cause strongSwan
to crash, resulting in a denial of service, or possibly bypass client and
server authentication.
Instructions: In general, a standard system update will make all the necessary changes.
Ubuntu
strongSwan vulnerability
vendor_ubuntu·2022-01-24
CVE-2021-45079 strongSwan vulnerability
Title: strongSwan vulnerability
Summary: strongSwan could crash or allow unintended access to network services.
Zhuowei Zhang discovered that stringSwan incorrectly handled EAP
authentication. A remote attacker could use this issue to cause strongSwan
to crash, resulting in a denial of service, or possibly bypass client and
server authentication.
Instructions: In general, a standard system update will make all the necessary changes.
Microsoft
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
vendor_msrc·2022-01-11·CVSS 9.1
CVE-2021-45079 [CRITICAL] CWE-476 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
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.
FAQ: Is Azure Linux the only Microsoft product that includes this open-source library and is therefore potentially affected by this vulnerability?
One of the main benefits to our customers who choose to use the Azure Linux distro is the commitment to keep it up to date with the most recent and most secure versions of the open source libraries with which the distro is composed. Microsoft is committed to transparency in this work which is why we began publishing CSAF/VEX in October 2025. See this blog post for more information.
Debian
CVE-2021-45079: strongswan - In strongSwan before 5.9.5, a malicious responder can send an EAP-Success messag...
vendor_debian·2021·CVSS 9.1
CVE-2021-45079 [CRITICAL] CVE-2021-45079: strongswan - In strongSwan before 5.9.5, a malicious responder can send an EAP-Success messag...
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.
Scope: local
bookworm: resolved (fixed in 5.9.5-1)
bullseye: resolved (fixed in 5.9.1-1+deb11u2)
forky: resolved (fixed in 5.9.5-1)
sid: resolved (fixed in 5.9.5-1)
trixie: resolved (fixed in 5.9.5-1)
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
2022-01-31
Published