CVE-2026-78135

MEDIUM

Published Sep 11, 2026 Modified Sep 16, 2026 CWE-841

Description

libcharon in strongSwan 5.9.7 through 6.0.7 mishandles behavioral workflow in the IKEv2 state machine. Because CREATE_CHILD_SA requests are mishandled, there can be an authentication bypass.

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CVSS v3.1 Score

5.6

MEDIUM

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

EPSS — Exploit Prediction

0.0034

Probability of exploitation

0.27%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-841 CWE-841

Affected Products

Vendor	Product	Versions
strongswan	strongswan	5.9.7 — 6.0.7

References

Advisories & Patches

https://github.com/strongswan/strongswan/releases/tag/6.1.0 https://www.strongswan.org/blog/2026/09/07/strongswan-vulnerability-(cve-2026-78135).html

Frequently Asked Questions

What is CVE-2026-78135? +

libcharon in strongSwan 5.9.7 through 6.0.7 mishandles behavioral workflow in the IKEv2 state machine. Because CREATE_CHILD_SA requests are mishandled, there can be an authentication bypass. It has a CVSS v3.1 base score of 5.6 (MEDIUM).

How severe is CVE-2026-78135? +

CVE-2026-78135 has a CVSS v3.1 score of 5.6 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0034, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-78135? +

CVE-2026-78135 affects products from strongswan, specifically: strongswan. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-78135? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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