# CVE-2026-78129: strongSwan infinite loop in PKCS#5 decryption

Source: https://junglewise.ai/threats/cve-2026-78129-strongswan-infinite-loop-in-pkcs-5-decryption  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-11. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-78129 · Severity: medium · CVSS 5.9 · Published 2026-09-11

strongSwan is an open-source IPsec implementation used to establish secure VPN connections and encrypted communications. A flaw in its handling of encrypted certificate containers allows a remote attacker to send a crafted message that causes the IKE daemon to consume CPU indefinitely or crash, disrupting VPN services and potentially affecting business continuity for organizations relying on this technology for secure remote access.

Technologies: [strongSwan](https://junglewise.ai/threats/technologies/strongswan). Vendors: [strongSwan](https://junglewise.ai/threats/vendors/strongswan).

## Quick answers

**Is CVE-2026-78129 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78129 being exploited in the wild.

**How severe is CVE-2026-78129?** Medium severity, with a CVSS score of 5.9, published 11 September 2026.

**Which products and versions are affected?** strongSwan 4.6.2 through 6.0.7.

**Is there a fix for CVE-2026-78129?** A patch was published on 2026-09-07: Fixed in strongSwan 6.1.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-78129 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-78129?** Check whether you run strongSwan at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an infinite loop / denial of service in the PKCS#5 implementation within libstrongswan. The root cause is missing validation of the iteration count, key length, and salt length parameters when decrypting PKCS#5-encrypted structures (e.g., PKCS#7 containers). An attacker can craft an encrypted PKCS#7 container with an astronomically large iteration count that, when processed, causes the decryption loop to block indefinitely. Additionally, an excessively large key length parsed as a 64-bit value without bounds can cause a stack buffer overflow via chunk_alloca(), leading to a crash. Since strongSwan 5.1.0, the pkcs7 plugin automatically attempts to decrypt containers without a password (to handle password-less PKCS#12 containers), making remote exploitation possible via IKEv1 certificate payloads. The attack is unauthenticated and requires only network reachability to an IKE daemon with IKEv1 enabled. Patch is available in strongSwan 6.1.0 released on 2026-09-07.

## Affected products

- strongSwan strongSwan 4.6.2 through 6.0.7

## Timeline

- 2026-09-07: disclosed
- 2026-09-07: patched: Fixed in strongSwan 6.1.0

## References

- [https://github.com/strongswan/strongswan/releases/tag/6.1.0](https://github.com/strongswan/strongswan/releases/tag/6.1.0)
- [https://www.strongswan.org/blog/2026/09/07/strongswan-vulnerability-(cve-2026-78129).html](https://www.strongswan.org/blog/2026/09/07/strongswan-vulnerability-(cve-2026-78129).html)

## Related threats

- [strongSwan libcharon authentication bypass in IKEv2 CREATE_CHILD_SA handling](https://junglewise.ai/threats/cve-2026-78135-strongswan-libcharon-authentication-bypass-in-ikev2-create-child)
- [strongSwan incorrect identity binding in EAP-PEAP and EAP-TTLS](https://junglewise.ai/threats/cve-2026-78134-strongswan-incorrect-identity-binding-in-eap-peap-and-eap-ttls)
- [strongSwan libcharon use-after-free in IKEv2 rekeying collision handling](https://junglewise.ai/threats/cve-2026-78133-strongswan-libcharon-use-after-free-in-ikev2-rekeying-collision)
- [strongSwan x509 plugin infinite loop in ietfAttrSyntax parsing](https://junglewise.ai/threats/cve-2026-78132-strongswan-x509-plugin-infinite-loop-in-ietfattrsyntax-parsing)
- [strongSwan x509 plugin memory leak in attribute certificate parsing](https://junglewise.ai/threats/cve-2026-78131-strongswan-x509-plugin-memory-leak-in-attribute-certificate)