Vulnerability Note VU#338343

strongSwan VPN charon server vulnerable to buffer underflow

Original Release date: 23 May 2018 | Last revised: 13 Jun 2018


strongSwan VPN's charon server prior to version 5.6.3 does not check packet length and may allow buffer underflow, resulting in denial of service.


CWE-124: Buffer Underwrite ('Buffer Underflow') - CVE-2018-5388

In stroke_socket.c, a missing packet length check could allow a buffer underflow, which may lead to resource exhaustion and denial of service while reading from the socket.

According to the vendor, an attacker must typically have local root permissions to access the socket. However, other accounts and groups such as the vpn group (if capability dropping in enabled, for example) may also have sufficient permissions, but this configuration does not appear to be the default behavior.


A remote attacker with local user credentials (possibly a normal user in the vpn group, or root) may be able to underflow the buffer and cause a denial of service.


Apply an update

StrongSwan version 5.6.3 and above contain a patch for this issue.

Vendor Information (Learn More)

VendorStatusDate NotifiedDate Updated
strongSwanAffected21 Mar 201824 May 2018
SUSE LinuxAffected23 May 201824 May 2018
Alpine LinuxUnknown23 May 201823 May 2018
Arch LinuxUnknown23 May 201823 May 2018
Arista Networks, Inc.Unknown23 May 201823 May 2018
ASP LinuxUnknown23 May 201823 May 2018
CentOSUnknown23 May 201823 May 2018
CoreOSUnknown23 May 201823 May 2018
Debian GNU/LinuxUnknown23 May 201823 May 2018
ENEAUnknown23 May 201823 May 2018
Fedora ProjectUnknown23 May 201823 May 2018
GeexboxUnknown23 May 201823 May 2018
Gentoo LinuxUnknown23 May 201823 May 2018
HomeSeerUnknown23 May 201823 May 2018
Micro FocusUnknown23 May 201823 May 2018
If you are a vendor and your product is affected, let us know.View More »

CVSS Metrics (Learn More)

Group Score Vector
Base 4.9 AV:N/AC:H/Au:S/C:N/I:N/A:C
Temporal 3.8 E:POC/RL:OF/RC:C
Environmental 3.9 CDP:ND/TD:ND/CR:ND/IR:ND/AR:ND



Thanks to Kevin Backhouse of Semmle Ltd. for reporting this vulnerability.

This document was written by Garret Wassermann.

Other Information

  • CVE IDs: CVE-2018-5388
  • Date Public: 22 May 2018
  • Date First Published: 23 May 2018
  • Date Last Updated: 13 Jun 2018
  • Document Revision: 39


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