Amazon Linux 2 (EOS) Security Advisory: ALAS2-2026-3991
Advisory Released Date: 2026-10-12
Advisory Updated Date: 2026-10-12
FAQs regarding Amazon Linux ALAS/CVE Severity
Issue summary: A certificate with many nameRelativeToCRLIssuer CRL
distribution points causes disproportionate heap growth when OpenSSL caches
X.509 extensions.
Impact summary: Receiving a crafted certificate from a malicious peer can lead
to significant memory pressure and possible Denial of Service in clients or
in 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 for
size of certificates accepted from the peer (~100 KiB) can result in allocation
of several hundred MiB of resident memory on the receiving side
during a normal TLS handshake. This may be enough to crash the client or
server, if multiple concurrent connections lead to similarly large memory
allocations.
The fix postpones processing of the CRL distribution points extensions in
certificates to the time when the processed value is required for CRL processing.
This avoids keeping large memory allocations for a long time when such
certificates are received.
FIPS impact: no
The affected code is outside the FIPS module boundary. (CVE-2026-35189)
Issue summary: The generic elliptic-curve scalar multiplication used for
ECDSA and SM2 signature operations with curves that do not have a dedicated
implementation leaks information about the secret nonce through timing.
Impact summary: An attacker able to measure signing times may learn
information about the per-signature secret nonce, which over many signatures
can, via a lattice / Hidden Number Problem attack, lead to recovery of the
private key.
CWE: CWE-208: Observable Timing Discrepancy
Description: The generic elliptic-curve scalar multiplication used for
curves that do not have a dedicated constant-time implementation pads the
secret scalar with non-constant-time BIGNUM operations, so the time taken
depends 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 of
measurements. The effect is largest for curves whose group order lies
on a machine-word boundary, such as brainpoolP384r1.
Applications using ECDSA signing over the Brainpool and other generic prime
curves, 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-time
implementations and are not affected.
FIPS Impact: no
The FIPS modules are not affected: the approved NIST curves used in the FIPS
provider have dedicated constant-time implementations and do not use the
affected code path. (CVE-2026-54872)
Issue summary: An established DTLS 1.2 association using an AEAD cipher suite
can be terminated by a single unauthenticated datagram whose encrypted
fragment is shorter than the mandatory explicit IV and authentication tag
overhead.
Impact summary: An attacker who can send a datagram that is routed to an
existing DTLS 1.2 association can tear that association down without knowing
any key material. This is a Denial of Service limited to the targeted
association. 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 cipher
suite carries an explicit IV followed by the ciphertext and an authentication
tag. When decrypting such a record the record layer passed the record length to
the cipher implementation before checking that the record was long enough to
contain the explicit IV and the tag. For a record shorter than that overhead the
cipher implementation rejected the impossible length, and the record layer
treated this as an internal failure and raised a fatal internal_error alert
instead of treating the record as one that failed authentication.
In TLS 1.2 the same record causes a fatal internal_error alert instead of the
expected bad_record_mac alert. Since any undecryptable record already
terminates a TLS connection, this is a protocol conformance issue rather than
a security issue in TLS.
The fix validates the record length against the explicit IV and tag length
before any AEAD processing, so that TLS reports bad_record_mac and DTLS
silently discards the record.
FIPS impact: no
The 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)
Affected Packages:
openssl11
Note:
This advisory is applicable to Amazon Linux 2 (AL2) Core repository. Visit this FAQ section for the difference between AL2 Core and AL2 Extras advisories.
Issue Correction:
Run yum update openssl11 or yum update --advisory ALAS2-2026-3991 to update your system.
aarch64:
openssl11-1.1.1zj-1.amzn2.0.1.aarch64
openssl11-libs-1.1.1zj-1.amzn2.0.1.aarch64
openssl11-devel-1.1.1zj-1.amzn2.0.1.aarch64
openssl11-static-1.1.1zj-1.amzn2.0.1.aarch64
openssl11-debuginfo-1.1.1zj-1.amzn2.0.1.aarch64
i686:
openssl11-1.1.1zj-1.amzn2.0.1.i686
openssl11-libs-1.1.1zj-1.amzn2.0.1.i686
openssl11-devel-1.1.1zj-1.amzn2.0.1.i686
openssl11-static-1.1.1zj-1.amzn2.0.1.i686
openssl11-debuginfo-1.1.1zj-1.amzn2.0.1.i686
src:
openssl11-1.1.1zj-1.amzn2.0.1.src
x86_64:
openssl11-1.1.1zj-1.amzn2.0.1.x86_64
openssl11-libs-1.1.1zj-1.amzn2.0.1.x86_64
openssl11-devel-1.1.1zj-1.amzn2.0.1.x86_64
openssl11-static-1.1.1zj-1.amzn2.0.1.x86_64
openssl11-debuginfo-1.1.1zj-1.amzn2.0.1.x86_64