ALAS2-2026-4029

Amazon Linux 2 (EOS) Security Advisory: ALAS2-2026-4029
Advisory Released Date: 2026-10-24
Advisory Updated Date: 2026-10-26
Severity: Important
Issue Overview:

A heap-based buffer overflow flaw was found in Cyrus SASL. The add_to_challenge() function in the DIGEST-MD5 plugin computes the size of the buffer needed for a challenge/response field before DIGEST-MD5 quoting is applied, but does not recompute that size when quoting (escaping special characters) makes the value longer. The under-sized buffer is then passed to strcat(), causing a heap-based out-of-bounds write whose size depends on attacker-controlled input. A malicious or on-path DIGEST-MD5 (or HTTP Digest) server can trigger this flaw in a connecting client by supplying a crafted challenge field, such as realm or nonce, most likely resulting in a crash of the client application. (CVE-2026-107161)


Affected Packages:

cyrus-sasl


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 cyrus-sasl or yum update --advisory ALAS2-2026-4029 to update your system.

New Packages:
aarch64:
    cyrus-sasl-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-lib-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-devel-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-gssapi-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-plain-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-md5-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-ntlm-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-sql-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-ldap-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-scram-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-gs2-2.1.26-24.amzn2.0.2.aarch64
    cyrus-sasl-debuginfo-2.1.26-24.amzn2.0.2.aarch64

i686:
    cyrus-sasl-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-lib-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-devel-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-gssapi-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-plain-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-md5-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-ntlm-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-sql-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-ldap-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-scram-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-gs2-2.1.26-24.amzn2.0.2.i686
    cyrus-sasl-debuginfo-2.1.26-24.amzn2.0.2.i686

src:
    cyrus-sasl-2.1.26-24.amzn2.0.2.src

x86_64:
    cyrus-sasl-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-lib-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-devel-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-gssapi-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-plain-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-md5-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-ntlm-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-sql-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-ldap-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-scram-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-gs2-2.1.26-24.amzn2.0.2.x86_64
    cyrus-sasl-debuginfo-2.1.26-24.amzn2.0.2.x86_64

Additional References

Red Hat: CVE-2026-107161

Mitre: CVE-2026-107161