Amazon Linux 2023 : runfinch-finch (ALAS2023-2026-1809)

critical Nessus Plugin ID 319847

Synopsis

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

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-1809 advisory.

An authenticated SSH client that repeatedly opened channels which were rejected by the server caused unbounded memory growth, eventually crashing the server process and affecting all connected users.
Rejected channels are now properly removed from the connection's internal state and released for garbage collection. (CVE-2026-39827)

When an SSH server authentication callback returned PartialSuccessError with non-nil Permissions, those permissions were silently discarded, potentially dropping certificate restrictions such as force-command after a second factor succeeded. Returning non-nil Permissions with PartialSuccessError now results in a connection error. (CVE-2026-39828)

The RSA and DSA public key parsers did not enforce size limits on key parameters. A crafted public key with an excessively large modulus or DSA parameter could cause several minutes of CPU consumption during signature verification. This could be triggered by unauthenticated clients during public key authentication. RSA moduli are now limited to 8192 bits, and DSA parameters are validated per FIPS 186-2.
(CVE-2026-39829)

A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop. The blocked goroutine could not be released by calling Close(), resulting in a resource leak per connection. Unsolicited global responses are now discarded. (CVE-2026-39830)

The Verify() method for FIDO/U2F security key types ([email protected], sk-ssh- [email protected]) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a no-touch-required extension in Permissions.Extensions from PublicKeyCallback. (CVE-2026-39831)

When adding a key to a remote agent constraint extensions such as [email protected] were not serialized in the request. Destination restrictions were silently stripped when forwarding keys, allowing unrestricted use of the key on the remote host. The client now serializes all constraint extensions. Additionally, the in-memory keyring returned by NewKeyring() now rejects keys with unsupported constraint extensions instead of silently ignoring them. (CVE-2026-39832)

The in-memory keyring returned by NewKeyring() silently accepted keys with the ConfirmBeforeUse constraint but never enforced it. The key would sign without any confirmation prompt, with no indication to the caller that the constraint was not in effect. NewKeyring() now returns an error when unsupported constraints are requested. (CVE-2026-39833)

When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation. (CVE-2026-39834)

SSH servers which use CertChecker as a public key callback without setting IsUserAuthority or IsHostAuthority could be caused to panic by a client presenting a certificate. CertChecker now returns an error instead of panicking when these callbacks are nil. (CVE-2026-39835)

Previously, a revoked 'SignatureKey' belonging to a CA was not correctly checked for revocation. Now, both the 'key' and 'key.SignatureKey' are checked for @revoked. (CVE-2026-42508)

Previously, CVE-2024-45337 fixed an authorization bypass for misused ssh server configurations; if any other type of callback is passed other than public key, then the source-address validation would be skipped. (CVE-2026-46595)

An incorrectly placed cast from bytes to int allowed for server-side panic in the AES-GCM packet decoder for well-crafted inputs. (CVE-2026-46597)

For certain crafted inputs, a 'ed25519.PrivateKey' was created by casting malformed wire bytes, leading to a panic when used. (CVE-2026-46598)

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 runfinch-finch --releasever 2023.12.20260608' or or 'dnf update --advisory ALAS2023-2026-1809 --releasever 2023.12.20260608' to update your system.

Plugin Details

Severity: Critical

ID: 319847

File Name: al2023_ALAS2023-2026-1809.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 6/8/2026

Updated: 6/8/2026

Supported Sensors: Continuous Assessment, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 8.1

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7

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

CVSS Score Source: CVE-2026-42508

CVSS v3

Risk Factor: Critical

Base Score: 10

Temporal Score: 8.7

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

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

CVSS Score Source: CVE-2026-46595

Vulnerability Information

CPE: cpe:/o:amazon:linux:2023, p-cpe:/a:amazon:linux:runfinch-finch

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

Exploit Ease: No known exploits are available

Patch Publication Date: 6/8/2026

Vulnerability Publication Date: 5/12/2026

Reference Information

CVE: CVE-2026-39827, CVE-2026-39828, CVE-2026-39829, CVE-2026-39830, CVE-2026-39831, CVE-2026-39832, CVE-2026-39833, CVE-2026-39834, CVE-2026-39835, CVE-2026-42508, CVE-2026-46595, CVE-2026-46597, CVE-2026-46598

IAVB: 2026-B-0120

Detections

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