ALAS2-2026-3389

References: CVE-2026-25680  CVE-2026-39829  CVE-2026-39830  CVE-2026-39831  CVE-2026-39833  CVE-2026-42508  CVE-2026-46595 
FAQs regarding Amazon Linux ALAS/CVE Severity

Issue Overview:

Parsing arbitrary HTML can consume excessive CPU time, possibly leading to denial of service. (CVE-2026-25680)

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 (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) 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)

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)

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)

Issue Correction:
Run yum update amazon-cloudwatch-agent or yum update --advisory ALAS2-2026-3389 to update your system.

New Packages:

aarch64:
    amazon-cloudwatch-agent-1.300067.1-1.amzn2.aarch64

src:
    amazon-cloudwatch-agent-1.300067.1-1.amzn2.src

x86_64:
    amazon-cloudwatch-agent-1.300067.1-1.amzn2.x86_64