Linux Distros Unpatched Vulnerability : CVE-2026-2673

high Nessus Plugin ID 302195

Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- Issue summary: An OpenSSL TLS 1.3 server may fail to negotiate the expected preferred key exchange group when its key exchange group configuration includes the default by using the 'DEFAULT' keyword. Impact summary: A less preferred key exchange may be used even when a more preferred group is supported by both client and server, if the group was not included among the client's initial predicated keyshares. This will sometimes be the case with the new hybrid post-quantum groups, if the client chooses to defer their use until specifically requested by the server. If an OpenSSL TLS 1.3 server's configuration uses the 'DEFAULT' keyword to interpolate the built-in default group list into its own configuration, perhaps adding or removing specific elements, then an implementation defect causes the 'DEFAULT' list to lose its 'tuple' structure, and all server-supported groups were treated as a single sufficiently secure 'tuple', with the server not sending a Hello Retry Request (HRR) even when a group in a more preferred tuple was mutually supported. As a result, the client and server might fail to negotiate a mutually supported post- quantum key agreement group, such as 'X25519MLKEM768', if the client's configuration results in only 'classical' groups (such as 'X25519' being the only ones in the client's initial keyshare prediction).
OpenSSL 3.5 and later support a new syntax for selecting the most preferred TLS 1.3 key agreement group on TLS servers. The old syntax had a single 'flat' list of groups, and treated all the supported groups as sufficiently secure. If any of the keyshares predicted by the client were supported by the server the most preferred among these was selected, even if other groups supported by the client, but not included in the list of predicted keyshares would have been more preferred, if included. The new syntax partitions the groups into distinct 'tuples' of roughly equivalent security. Within each tuple the most preferred group included among the client's predicted keyshares is chosen, but if the client supports a group from a more preferred tuple, but did not predict any corresponding keyshares, the server will ask the client to retry the ClientHello (by issuing a Hello Retry Request or HRR) with the most preferred mutually supported group. The above works as expected when the server's configuration uses the built-in default group list, or explicitly defines its own list by directly defining the various desired groups and group 'tuples'. No OpenSSL FIPS modules are affected by this issue, the code in question lies outside the FIPS boundary.
OpenSSL 3.6 and 3.5 are vulnerable to this issue. OpenSSL 3.6 users should upgrade to OpenSSL 3.6.2 once it is released. OpenSSL 3.5 users should upgrade to OpenSSL 3.5.6 once it is released. OpenSSL 3.4, 3.3, 3.0, 1.0.2 and 1.1.1 are not affected by this issue. (CVE-2026-2673)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: High

ID: 302195

File Name: unpatched_CVE_2026_2673.nasl

Version: 1.2

Type: local

Agent: unix

Family: Misc.

Published: 3/13/2026

Updated: 3/13/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 2.9

CVSS v2

Risk Factor: Medium

Base Score: 6.4

Temporal Score: 5.4

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

CVSS Score Source: CVE-2026-2673

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.9

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

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

Vulnerability Information

CPE: cpe:/o:centos:centos:7, cpe:/o:redhat:enterprise_linux:6, cpe:/o:redhat:enterprise_linux:7, cpe:/o:redhat:enterprise_linux:8, p-cpe:/a:centos:centos:openssl, p-cpe:/a:centos:centos:openssl-devel, p-cpe:/a:centos:centos:openssl-perl, p-cpe:/a:centos:centos:openssl-static, p-cpe:/a:centos:centos:openssl098e, p-cpe:/a:centos:centos:openssl-libs, p-cpe:/a:debian:debian_linux:openssl, p-cpe:/a:redhat:enterprise_linux:openssl, p-cpe:/a:redhat:enterprise_linux:openssl-devel, p-cpe:/a:redhat:enterprise_linux:openssl-libs, p-cpe:/a:redhat:enterprise_linux:openssl-perl, p-cpe:/a:redhat:enterprise_linux:openssl-static, p-cpe:/a:redhat:enterprise_linux:openssl098e, cpe:/o:centos:centos:8, cpe:/o:redhat:enterprise_linux:9, p-cpe:/a:redhat:enterprise_linux:compat-openssl11, p-cpe:/a:redhat:enterprise_linux:compat-openssl10, p-cpe:/a:centos:centos:compat-openssl11, cpe:/o:debian:debian_linux:13.0, cpe:/o:redhat:enterprise_linux:10, p-cpe:/a:centos:centos:compat-openssl10, p-cpe:/a:centos:centos:mingw32-openssl, p-cpe:/a:centos:centos:mingw64-openssl, p-cpe:/a:redhat:enterprise_linux:mingw32-openssl, p-cpe:/a:redhat:enterprise_linux:mingw64-openssl, cpe:/o:debian:debian_linux:14.0, p-cpe:/a:redhat:enterprise_linux:openssl-fips-provider, p-cpe:/a:redhat:enterprise_linux:openssl-fips-provider-so, p-cpe:/a:centos:centos:openssl-fips-provider, p-cpe:/a:centos:centos:openssl-fips-provider-so

Required KB Items: Host/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 3/13/2026

Reference Information

CVE: CVE-2026-2673

Detections

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