Amazon Linux 2023 : openssl, openssl-devel, openssl-fips-provider-latest (ALAS2023-2026-3204)

high Nessus Plugin ID 365185

Synopsis

The remote Amazon Linux 2023 host is missing a security update.

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3204 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 OpenSSL QUIC server, when configured to not preform addressvalidation, can be forced to count incoming packets multiple times in itsunvalidated credit computation, leading to a violation of the RFC 9000unvalidated connection amplification limit of 3 times the amount of datareceived.

Impact summary: A remote attacker able to spoof packets to a server using theOpenSSL QUIC implementation might use the server for an amplification ofa DDoS attack.

CWE: CWE-440: Expected Behavior Violation

Description: OpenSSL's QUIC stack, when operating as a server, enforces clientaddress validation (RFC 9000, Section 8), to confirm the peer address is notused for a traffic amplification attack. If this feature is disabled on theserver, the QUIC stack limits the amount of server data that can be sent to 3times the amount of data received from the peer address, until such time as theTLS handshake is completed.

The OpenSSL QUIC server, when operating in non-validation mode, adds thelength of the whole datagram received to the unvalidated credit limit whenprocessing each QUIC packet in the datagram. A remote peer may,after establishing a connection with an initial client hello frame, send asubsequent datagram containing multiple QUIC packets, leading the server toaccount the entire datagram length for each packet in the datagram, resultingin the server believing that the peer has sent more data than it actually has,thereby violating the 3x amplification limit mandated by the RFC.

FIPS impact: noAs the QUIC stack lives outside the FIPS module boundary, no FIPS modulesare affected by this CVE. (CVE-2026-35191)

Issue summary: The QUIC stream reassembly algorithm performance deterioratesprogressively as packets are arriving out of order. The worst case hasa quadratic complexity proportional to the number of stream frames kept inthe buffer for the received stream data.

Impact summary: A remote QUIC peer that completes the handshake can createa connection-scoped CPU pressure and potentially a Denial of Service usingcompliant STREAM frames inside the advertised receive window, with lowattacker bandwidth.

CWE: CWE-407: Inefficient Algorithmic Complexity

Description: OpenSSL manages received QUIC stream fragments using adoubly-linked list. While it optimizes for append operations (at the end ofthe list), it falls back to a head-to-tail linear search for any fragmentthat does not immediately follow the current `tail`.

By manipulating the sequence of offsets, an attacker can force the serverto perform O(n^2) operations, consuming excessive CPU time for theQUIC process.

FIPS impact: noThe FIPS module is not affected as the QUIC implementation is outside ofthe OpenSSL FIPS module boundary. (CVE-2026-42772)

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: QUIC process may keep memory for QUIC packetbuffer for much longer period than necessary.

Impact summary: Remote peer can exploit this vulnerabilityby sending maliciously crafted packets, making the localQUIC stack to keep the memory for packet buffers allocated.The time for which the memory remains allocated is entirelyunder the control of the potentially malicious remote peer.

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

Description: To save copy operation from the packet buffer to thestream reassemble buffer the QUIC stack leaves the stream dataon the packet buffer waiting to be copied to a buffer providedby the local receiving application. The QUIC stack releasesa reference to the packet buffer only after the data are copiedto the application buffer. This design is more efficient forlegitimate data transfers but enables an attacker to allocate a lotmore memory than actually required by the data kept in the receivingstream buffer.

To mitigate the vulnerability, the QUIC stack now calculatesand monitors memory overhead for every stream.
The memory overheadfor a single stream frame is calculated as a difference between thesize of the whole packet that carries the stream frame and the sizeof the stream frame itself. The memory overhead for a single streamframe is added to the total (cumulative) memory overhead QUIC stackkeeps for each stream.
Once the cumulative memory overhead exceeds64kB, the QUIC stack moves the stream frame data from the packetbuffer to the stream buffer, starting with the next packet received.

FIPS impact: noThe FIPS module is not affected as the QUIC implementation is outside ofthe OpenSSL FIPS module boundary. (CVE-2026-54873)

Issue summary: A TLS server that calls SSL_set_SSL_CTX() to switch aconnection to a different SSL_CTX part way through a handshake may accessmemory beyond the end of an internal array if the replacement context knowsabout more provider signature algorithms than the context the connection wascreated from.
Applications which never call SSL_set_SSL_CTX() are notaffected.

Impact summary: A remote peer may be able to cause a small out-of-boundsread, and in some circumstances a fixed-value out-of-bounds write, on theserver heap. This may lead to a Denial of Service.

CWE: CWE-787: Out-of-bounds Write

Description: A TLS connection records how many certificate slots it haswhen it is created, taken from the SSL_CTX that created it: the built-incertificate types plus one slot for each provider TLS-SIGALG entry thatcontext was aware of. That count sizes an internal array of per-slotcertificate validity flags.

An application may replace a connection's SSL_CTX part way through thehandshake by calling SSL_set_SSL_CTX(), most commonly from a servernamecallback in order to serve a different virtual host.
Doing so did notrefresh the recorded count. A provider signature algorithm's slot index isits position in the list of whichever context resolves it, so if thereplacement context is aware of more of them than the original, analgorithm offered by the peer can resolve to an index beyond the end of thearray. Processing the peer's signature algorithms then reads one four byteword past the end for each such algorithm and, where the word read is zero,writes a fixed value over it. A peer offering many of them can corrupt heapmetadata and abort the process.

Only provider signature algorithms which occupy one of the excess slots,and which the server also has configured, have this effect. Codepoints thereplacement context does not recognise are discarded without being resolvedto a slot, and provider signature algorithms are usable only from TLS 1.3.

The two contexts must therefore be aware of different numbers of providersignature algorithms, which requires separate library contexts, a providerloaded between the two being created, or providers which differ in whatthey advertise - in 4.0, for example, the default provider advertises SM2where the FIPS provider does not. A deployment meeting the condition isalso unable to negotiate the affected algorithms with legitimate clients,since the same stale count hides the corresponding certificates, so themisconfiguration is likely to be noticed. For that reason, and because theconfiguration is not the default, this issue has been assessed as Lowseverity.

FIPS impact: noNo FIPS modules are affected by this issue as the affected code is outsidethe OpenSSL FIPS module boundary. (CVE-2026-72897)

Issue summary: OpenSSL QUIC stack does not enforce connectionlevel flow control for streams. Remote peers may send more bytesas long as they fit within the stream flow control limits.

Impact summary: A malicious remote peer may exploit the lack of connectionflow control for streams to make the QUIC stack receive ~100MB of memoryinstead of 768 KiB (default flow control window size).

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

Description: The local QUIC stack advertises two flow control limitsto its remote peer: stream flow control limit and connection flowcontrol limit. The remote peer must follow both limits when transmittingstream data.

Whenever the local QUIC stack receives a stream frame, it validatesthat the size of the received stream frame stays within flow control limits.If either limit is exceeded (stream level or connection level), thenthe QUIC stack must close the connection with a flow control error.

The vulnerable OpenSSL QUIC stack enforces the stream-level but notthe connection-level limit. To exploit the issue, three conditions must be met:- the remote peer opens several streams- each stream must stay within the stream-level flow control limit- there must be no zero-offset byte sent on any of the streams(to prevent the vulnerable QUIC stack from consuming data).By meeting the conditions above, the remote peer may make the local stackallocate 2 x MAX_STREAMS x (stream flow control limit) bytesof memory.
MAX_STREAMS defaults to 100, and the limit applies to bothbidirectional and unidirectional streams, making it 200 in total. The defaultflow control window for a stream is 512kB. The remote peer mayforce the vulnerable QUIC stack to allocate 100MB of heap per connection.

FIPS impact: noThe FIPS module is not affected as the QUIC implementation is outside ofthe OpenSSL FIPS module boundary. (CVE-2026-75804)

Issue summary: A CMP client that requests certificate revocation on the basisof a PKCS#10 CSR may dereference a NULL pointer and terminate abnormally whenprocessing a crafted revocation response.

Impact summary: The NULL pointer dereference happens on a read whichleads to a crash and a Denial of Service for the affected client application.

CWE: CWE-476: NULL-pointer dereference

Description: A CMP client revoking a certificate has to tell the server whichcertificate to revoke, and may do so by supplying a PKCS#10 CSR instead of thecertificate itself or its issuer name and serial number. This is'openssl cmp -cmd rr -csr <file>' on the command line, orOSSL_CMP_exec_RR_ses() with the certificate supplied viaOSSL_CMP_CTX_set1_p10CSR() through the API.

A CSR does not contain the issuer name and serial number of the certificate,so the client does not send them. A server may optionally name thecertificate it revoked in its response, and the client then compares thatname against what it sent. Having sent neither an issuer name nor a serialnumber, it has nothing to compare against, and a server returning a speciallycrafted name causes the client to read from a NULL pointer and crash.

The revocation response is checked for valid message protection beforethe affected code is reached, so an attacker must be a malicious orcompromised CMP server, or a man-in-the-middle in possession of thesecret used for message protection. Clients that identify the certificateto be revoked by a certificate or by issuer and serial number ratherthan by a PKCS#10 CSR are not affected.

FIPS impact: noNo FIPS modules are affected by this issue, as the CMP protocolimplementation is outside the OpenSSL FIPS module boundary. (CVE-2026-75805)

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)

Issue summary: A malicious remote peer may flood the local QUICstack with NEW_CONNECTION_ID frames by avoiding a limit check onhow many connection IDs the remote QUIC stack can use.

Impact summary: The local QUIC stack sends a RETIRE_CONN_ID framefor every NEW_CONNECTION_ID frame it receives. The RETIRE_CONN_IDframe is dispatched via the Control Frame Queue (CFQ). If the remotepeer also withholds ACKs, then it can force the local stackto allocate ~400MB (depending on ACK delay).

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

Description: RFC 9000 sections 5.1.1 and 5.1.2 [1] describe the mechanismby which a remote peer can notify the local QUIC stack to change thedestination connection ID (a.k.a. CID) the local stack uses toidentify the connection at the remote peer. Each CID is associatedwith a sequence number. The sequence number is transmittedin NEW_CONNECTION_ID and RETIRE_CONNECTION_ID frames to identify the CIDwhich is being either associated with a connection or retired.

The remote peer sends a NEW_CONNECTION_ID frame to let the local stack knowa new CID is being associated with an existing connection. TheNEW_CONNECTION_ID frame carries the new CID, its sequence number, and theretire-prior-to number. The retire-prior-to identifies existingCIDs that are to be retired. The local QUIC stack must send aRETIRE_CONNECTION_ID for every destination CID whose sequence numberis less than retire-prior-to. The CID becomes retired after thelocal stack receives an ACK for its RETIRE_CONNECTION_ID frame.

Although the OpenSSL QUIC stack supports at most one destination CIDfor every connection, it can be tricked into processing more thanone RETIRE_CONNECTION_ID frame per connection. The OpenSSL QUICstack currently retires the destination CID as soon as it receivesthe NEW_CONNECTION_ID, while in fact the destination CID mustbe retired after an ACK for the RETIRE_CONNECTION_ID frame is received.Correcting the flawed logic also fixes the backlog growth.

[1] https://datatracker.ietf.org/doc/html/rfc9000#name-issuing-connection-ids

FIPS impact: noThe FIPS module is not affected as the QUIC implementation is outside ofthe OpenSSL FIPS module boundary. (CVE-2026-84784)

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 'dnf update openssl --releasever 2023.12.20261012' or or 'dnf update --advisory ALAS2023-2026-3204 --releasever 2023.12.20261012' to update your system.

Plugin Details

Severity: High

ID: 365185

File Name: al2023_ALAS2023-2026-3204.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:2023, p-cpe:/a:amazon:linux:openssl-debuginfo, p-cpe:/a:amazon:linux:openssl-debugsource, p-cpe:/a:amazon:linux:openssl-devel, p-cpe:/a:amazon:linux:openssl-fips-provider-latest-debuginfo, p-cpe:/a:amazon:linux:openssl-fips-provider-latest, p-cpe:/a:amazon:linux:openssl-libs-debuginfo, p-cpe:/a:amazon:linux:openssl-libs, p-cpe:/a:amazon:linux:openssl-perl, p-cpe:/a:amazon:linux:openssl-snapsafe-libs-debuginfo, p-cpe:/a:amazon:linux:openssl-snapsafe-libs, p-cpe:/a:amazon:linux:openssl

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-2026-35191, CVE-2026-42772, CVE-2026-54872, CVE-2026-54873, CVE-2026-72897, CVE-2026-75804, CVE-2026-75805, CVE-2026-75806, CVE-2026-84782, CVE-2026-84784

IAVA: 2026-A-1072

Detections

Analytics