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AlmaLinux 9.6 [TuxCare] Security Update: libreswan Multiple Vulnerabilities (ALMALINUX9.6:CLSA-2026:1784305067)

medium Nessus Plugin ID 361737

Synopsis

The AlmaLinux host is missing one or more security updates.

Description

The AlmaLinux 9.6 host has a package installed that is affected by multiple vulnerabilities as referenced in the TuxCare ALMALINUX9.6:CLSA-2026:1784305067 advisory.

 - Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation.
 Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG 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 remote IKE peers are not affected. (CVE-2026-50721)

 - 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. (CVE-2026-50722)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected libreswan package based on the guidance in TuxCare advisory ALMALINUX9.6:CLSA-2026:1784305067.

See Also

https://cve.tuxcare.com/els/releases/CLSA-2026:1784305067

http://www.nessus.org/u?e36f6d77

Plugin Details

Severity: Medium

ID: 361737

File Name: tuxcare_alma_linux_9.6_CLSA-2026-1784305067.nasl

Version: 1.1

Type: Local

Published: 10/1/2026

Updated: 10/1/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.68

Vendor

Vendor Severity: Moderate

CVSS v2

Risk Factor: Medium

Base Score: 5.4

Temporal Score: 4

Vector: CVSS2#AV:N/AC:H/Au:N/C:N/I:N/A:C

CVSS Score Source: CVE-2026-50722

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.2

Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/AlmaLinux/release, Host/AlmaLinux/rpm-list, Host/OS/extended-third-party

Exploit Ease: No known exploits are available

Patch Publication Date: 7/17/2026

Vulnerability Publication Date: 7/2/2026

Reference Information

CVE: CVE-2026-50721, CVE-2026-50722

CLSA: 2026:1784305067