strongSwan: Integer Underflow (Wrap or Wraparound)
CVE-2026-25075 is a high-severity integer underflow (wrap or wraparound) vulnerability in strongSwan, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 6.0.5 as the first without the flaw, so updating strongSwan to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 1.07% chance of exploitation within 30 days, higher than 66% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update strongSwan to 6.0.5 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| strongSwan | strongSwan | 4.5.0 up to, but not including, 6.0.5 | 6.0.5 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.7 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 7.5 | High | CNA (vulncheck.com) |
Official description
strongSwan versions 4.5.0 prior to 6.0.5 contain an integer underflow vulnerability in the EAP-TTLS AVP parser that allows unauthenticated remote attackers to cause a denial of service by sending crafted AVP data with invalid length fields during IKEv2 authentication. Attackers can exploit the failure to validate AVP length fields before subtraction to trigger excessive memory allocation or NULL pointer dereference, crashing the charon IKE daemon.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Integer Underflow (Wrap or Wraparound)
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.
More Integer Underflow (Wrap or Wraparound) vulnerabilities (CWE-191)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
- strongswan.org/blog/2026/03/23/strongswan-6.0.5-released.html
- strongswan.org/blog/2026/03/23/strongswan-vulnerability-(cve-2026-25075).html
- vulncheck.com/advisories/strongswan-eap-ttls-avp-parsing-integer-underflow
- y637f9qq2x.com/posts/cve-2026-25075/
- lists.debian.org/debian-lts-announce/2026/03/msg00016.html
Other vulnerabilities in strongSwan
- 7.3 High severity
- 7.1 High severity
- 7.5 High severity
- 8.1 High severity
- 9.8 Critical severity
- 9.8 Critical severity
Recent Integer Underflow (Wrap or Wraparound) vulnerabilities
- 9.1 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.5 High severity
- 8.8 High severity
- 8.1 High severity
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