Vulnerability · Published Jul 2, 2026 · Assigned by libreswan
CVE-2026-50722IKEv2 Denial of Service via RSA-SHA1 (PKCS#1 RSASSA-PKCS1-v1_5) authentication payload
High 7.5
In plain English
A high-severity security flaw in libreswan from The Libreswan Project. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Libreswan, via the function RSA_authenticate_hash_signature_pkcs1_1_5_rsa(), did not correctly verify the DER encoding of the ASN.1 digest when the IKEv2 AUTH payload was encoded using RSASSA-PKCS1-v1_5 (RFC 8017). A remote attacker can use a variation on the Bleichenbacher attack to forge the AUTH payload when small public exponents are used (e.g., e=3), leading to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the AUTH payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of the remote IKE peer are not affected.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | libreswan | 5.3.2-1.el10_2 | ALSA-2026:46398 |
| AlmaLinux:8 | libreswan | 4.12-2.el8_10.6 | ALSA-2026:46396 |
| AlmaLinux:9 | libreswan | 4.15-10.el9_8 | ALSA-2026:46397 |
| AlmaLinux:10 | libreswan-minimal | 5.3.2-1.el10_2 | ALSA-2026:46398 |
| Alpine:v3.23 | libreswan | 5.3.3-r0 | ALPINE-CVE-2026-50722 |
| Alpine:v3.24 | libreswan | 5.3.2-r0 | ALPINE-CVE-2026-50722 |
| Debian:12 | libreswan | no fix listed | DEBIAN-CVE-2026-50722 |
| Debian:13 | libreswan | no fix listed | DEBIAN-CVE-2026-50722 |
| Rocky Linux:10 | libreswan | 0:5.3.2-1.el10_2 | RLSA-2026:46398 |
| Rocky Linux:8 | libreswan | 0:4.12-2.el8_10.6 | RLSA-2026:46396 |
| Rocky Linux:9 | libreswan | 0:4.15-10.el9_8 | RLSA-2026:46397 |
| Ubuntu:22.04:LTS | libreswan | no fix listed | UBUNTU-CVE-2026-50722 |
| Ubuntu:24.04:LTS | libreswan | no fix listed | UBUNTU-CVE-2026-50722 |
| Ubuntu:25.10 | libreswan | no fix listed | UBUNTU-CVE-2026-50722 |
| Ubuntu:26.04:LTS | libreswan | no fix listed | UBUNTU-CVE-2026-50722 |
| Ubuntu:26.10 | libreswan | no fix listed | UBUNTU-CVE-2026-50722 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| The Libreswan Project | libreswan | 0 – through 5.3 |
Weakness: CWE-347, CWE-617 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- Libreswan Security Advisory CVE-2026-50722 vendor-advisory
- Libreswan CVE-2026-50722 Patches patch
- Related: CVE-2026-50721 (IKEv1 variant) related
- RFC 8017 - PKCS #1: RSA Cryptography Specifications Version 2.2 technical-description