Amazon Linux 2 : openssl11 (ALAS-2026-3991)

high Nessus Plugin ID 365208

Synopsis

The remote Amazon Linux 2 host is missing a security update.

Description

The version of openssl11 installed on the remote host is prior to 1.1.1zj-1. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3991 advisory.

Issue summary: A certificate with many nameRelativeToCRLIssuer CRLdistribution points causes disproportionate heap growth when OpenSSL cachesX.509 extensions.

Impact summary: Receiving a crafted certificate from a malicious peer can leadto significant memory pressure and possible Denial of Service in clients orin servers that solicit client certificates.

CWE: CWE-770: Allocation of Resources Without Limits or Throttling

Description: A certificate or a set of certificates that fits under the limit forsize of certificates accepted from the peer (~100 KiB) can result in allocationof several hundred MiB of resident memory on the receiving sideduring a normal TLS handshake. This may be enough to crash the client orserver, if multiple concurrent connections lead to similarly large memoryallocations.

The fix postpones processing of the CRL distribution points extensions incertificates to the time when the processed value is required for CRL processing.This avoids keeping large memory allocations for a long time when suchcertificates are received.

FIPS impact: noThe affected code is outside the FIPS module boundary. (CVE-2026-35189)

Issue summary: The generic elliptic-curve scalar multiplication used forECDSA and SM2 signature operations with curves that do not have a dedicatedimplementation leaks information about the secret nonce through timing.

Impact summary: An attacker able to measure signing times may learninformation about the per-signature secret nonce, which over many signaturescan, via a lattice / Hidden Number Problem attack, lead to recovery of theprivate key.

CWE: CWE-208: Observable Timing Discrepancy

Description: The generic elliptic-curve scalar multiplication used forcurves that do not have a dedicated constant-time implementation pads thesecret scalar with non-constant-time BIGNUM operations, so the time takendepends on the value of the secret scalar derived from the ECDSA and SM2 nonce.

The leak is very small; observing it requires a large number ofmeasurements. The effect is largest for curves whose group order lieson a machine-word boundary, such as brainpoolP384r1.

Applications using ECDSA signing over the Brainpool and other generic primecurves, and SM2 signing on platforms that use the generic implementation,are vulnerable to this issue.

The NIST curves P-256, P-384 and P-521 use dedicated constant-timeimplementations and are not affected.

FIPS Impact: noThe FIPS modules are not affected: the approved NIST curves used in the FIPSprovider have dedicated constant-time implementations and do not use theaffected code path. (CVE-2026-54872)

Issue summary: An established DTLS 1.2 association using an AEAD cipher suitecan be terminated by a single unauthenticated datagram whose encryptedfragment is shorter than the mandatory explicit IV and authentication tagoverhead.

Impact summary: An attacker who can send a datagram that is routed to anexisting DTLS 1.2 association can tear that association down without knowingany key material. This is a Denial of Service limited to the targetedassociation. There is no memory safety or confidentiality impact.

CWE: CWE-1284: Improper Validation of Specified Quantity in Input

Description: In TLS 1.2 and DTLS 1.2 every record protected by an AEAD ciphersuite carries an explicit IV followed by the ciphertext and an authenticationtag. When decrypting such a record the record layer passed the record length tothe cipher implementation before checking that the record was long enough tocontain the explicit IV and the tag. For a record shorter than that overhead thecipher implementation rejected the impossible length, and the record layertreated this as an internal failure and raised a fatal internal_error alertinstead of treating the record as one that failed authentication.

In TLS 1.2 the same record causes a fatal internal_error alert instead of theexpected bad_record_mac alert. Since any undecryptable record alreadyterminates a TLS connection, this is a protocol conformance issue rather thana security issue in TLS.

The fix validates the record length against the explicit IV and tag lengthbefore any AEAD processing, so that TLS reports bad_record_mac and DTLSsilently discards the record.

FIPS impact: noThe affected code is outside the FIPS module boundary. (CVE-2026-75806)

A flaw was found in OpenSSL. The Datagram Transport Layer Security (DTLS) retransmission mechanism fails to properly handle handshake message writes that are suspended before completion. A remote attacker could exploit this vulnerability during handshake message retransmission, causing OpenSSL to read past the message buffer or overwrite internal state required to resume writing. This issue can result in information disclosure through out-of-bounds memory reads or cause a Denial of Service (DoS) by crashing the process. (CVE-2026-84782)

Tenable has extracted the preceding description block directly from the tested product security advisory.

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

Solution

Run 'yum update openssl11' or or 'yum update --advisory ALAS2-2026-3991' to update your system.

Plugin Details

Severity: High

ID: 365208

File Name: al2_ALAS-2026-3991.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 10/12/2026

Updated: 10/12/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Continuous Assessment, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.5

Percentile: 96.46

CVSS v2

Risk Factor: High

Base Score: 8.5

Temporal Score: 6.3

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

CVSS Score Source: CVE-2026-84782

CVSS v3

Risk Factor: High

Base Score: 8.2

Temporal Score: 7.1

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

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

Vulnerability Information

CPE: cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:openssl11-debuginfo, p-cpe:/a:amazon:linux:openssl11-devel, p-cpe:/a:amazon:linux:openssl11-libs, p-cpe:/a:amazon:linux:openssl11-static, p-cpe:/a:amazon:linux:openssl11

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 10/12/2026

Vulnerability Publication Date: 9/29/2026

Reference Information

CVE: CVE-2026-35189, CVE-2026-54872, CVE-2026-75806, CVE-2026-84782

IAVA: 2026-A-1072

Detections

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