OpenSSL 3.6.0 < 3.6.2 Multiple Vulnerabilities

critical Nessus Plugin ID 302501

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Synopsis

The remote service is affected by multiple vulnerabilities.

Description

The version of OpenSSL installed on the remote host is prior to 3.6.2. It is, therefore, affected by multiple vulnerabilities as referenced in the 3.6.2 advisory.

- 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)

- Debian Linux - openssl - None Red Hat Enterprise Linux - openssl: openssl: Information Disclosure from Uninitialized Memory via Invalid RSA Public Key (CVE-2026-31790)

- Debian Linux - openssl - None (CVE-2026-28389, CVE-2026-28390, CVE-2026-31789)

- Issue summary: When a delta CRL that contains a Delta CRL Indicator extension is processed a NULL pointer dereference might happen if the required CRL Number extension is missing. Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application. When CRL processing and delta CRL processing is enabled during X.509 certificate verification, the delta CRL processing does not check whether the CRL Number extension is NULL before dereferencing it. When a malformed delta CRL file is being processed, this parameter can be NULL, causing a NULL pointer dereference. Exploiting this issue requires the X509_V_FLAG_USE_DELTAS flag to be enabled in the verification context, the certificate being verified to contain a freshestCRL extension or the base CRL to have the EXFLAG_FRESHEST flag set, and an attacker to provide a malformed CRL to an application that processes it. The vulnerability is limited to Denial of Service and cannot be escalated to achieve code execution or memory disclosure. For that reason the issue was assessed as Low severity according to our Security Policy. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary. Fixed in OpenSSL 3.6.2 (Affected since 3.6.0).
(CVE-2026-28388)

- Issue summary: An uncommon configuration of clients performing DANE TLSA-based server authentication, when paired with uncommon server DANE TLSA records, may result in a use-after-free and/or double-free on the client side. Impact summary: A use after free can have a range of potential consequences such as the corruption of valid data, crashes or execution of arbitrary code. However, the issue only affects clients that make use of TLSA records with both the PKIX-TA(0/PKIX-EE(1) certificate usages and the DANE-TA(2) certificate usage. By far the most common deployment of DANE is in SMTP MTAs for which RFC7672 recommends that clients treat as 'unusable' any TLSA records that have the PKIX certificate usages. These SMTP (or other similar) clients are not vulnerable to this issue. Conversely, any clients that support only the PKIX usages, and ignore the DANE-TA(2) usage are also not vulnerable. The client would also need to be communicating with a server that publishes a TLSA RRset with both types of TLSA records. No FIPS modules are affected by this issue, the problem code is outside the FIPS module boundary. Fixed in OpenSSL 3.6.2 (Affected since 3.6.0). (CVE-2026-28387)

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

Solution

Upgrade to OpenSSL version 3.6.2 or later.

Plugin Details

Severity: Critical

ID: 302501

File Name: openssl_3_6_2.nasl

Version: 1.5

Type: Combined

Agent: windows, macosx, unix

Family: Web Servers

Published: 3/16/2026

Updated: 4/14/2026

Configuration: Enable thorough checks (optional)

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

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

CVSS Score Source: CVE-2026-2673

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 7.9

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

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

CVSS Score Source: CVE-2026-28386

Vulnerability Information

CPE: cpe:/a:openssl:openssl

Required KB Items: installed_sw/OpenSSL

Exploit Ease: No known exploits are available

Patch Publication Date: 3/13/2026

Vulnerability Publication Date: 3/13/2026

Reference Information

CVE: CVE-2026-2673, CVE-2026-28386, CVE-2026-28387, CVE-2026-28388, CVE-2026-28389, CVE-2026-28390, CVE-2026-31789, CVE-2026-31790

IAVA: 2026-A-0308

Detections

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