CVE-2026-50722
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.
Does this matter?
Lower severity and a low EPSS score (0.35%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 5.9 MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.35% probability · 28th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-347, CWE-617
- Affected
- libreswan/libreswan
- Source
- d42dc95b-23f1-4e06-9076-20753a0fb0df
References
- https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txtVendor Advisory, Mailing List
- https://libreswan.org/security/CVE-2026-50722/Vendor Advisory
- https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txtVendor Advisory
- https://www.rfc-editor.org/rfc/rfc8017Technical Description
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.