Ubuntu Linux - [Stack-based Buffer Overflow in mmpstrucdata rsyslog plugin]

The remote Debian 12 host has packages installed that are affected by multiple vulnerabilities as referenced in the dla-4891 advisory.

    - -------------------------------------------------------------------------     Debian LTS Advisory DLA-4891-1                debian-lts@lists.debian.org     https://www.debian.org/lts/security/                          Abhijith PA     November 11, 2026                             https://wiki.debian.org/LTS
    - -------------------------------------------------------------------------

    Package        : rsyslog     Version        : 8.2302.0-1+deb12u2     CVE ID         : CVE-2026-19654 CVE-2026-61548 CVE-2026-78002 CVE-2026-93403

    Several vulnerabilities were discovered in rsyslog, system and kernel     logging daemon.

    CVE-2026-19654

        An unauthenticated remote peer may lead rsyslogd to crash due to a         flaw in the optional imptcp module. A crafted input sequence         during oversize-frame recovery can cause an invalid internal         message length and terminate rsyslogd.

    CVE-2026-61548

        A remote unauthenticated attacker whose crafted RFC5424 message         reaches an action using mmpstrucdata can provide a structured-data         parameter larger than that buffer when MaxMessageSize permits it,         causing an attacker-controlled stack overwrite.

    CVE-2026-78002

        An unauthenticated remote attacker can trigger a heap buffer         overflow in the RainerScript `replace()` function by sending         specially crafted syslog messages. This vulnerability arises from         an incorrect buffer size calculation during string replacement,         causing memory corruption.

    CVE-2026-93403

        a stack-based buffer overflow in the mmpstrucdata output         module. An unauthenticated network sender who can deliver a         crafted RFC 5424 message to an affected rsyslog instance can cause         rsyslogd to terminate, resulting in denial of service.

    For Debian 12 bookworm, these problems have been fixed in version     8.2302.0-1+deb12u2.

    We recommend that you upgrade your rsyslog packages.

    For the detailed security status of rsyslog please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/rsyslog

    Further information about Debian LTS security advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://wiki.debian.org/LTS

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - A unauthenticated remote peer may lead rsyslogd to crash due to a flaw in the optional imptcp module. A
    crafted input sequence during oversize-frame recovery can cause an invalid internal message length and
    terminate rsyslogd. No confidentiality or integrity impact, privilege escalation, or code execution has
    been identified. imtcp and the default imptcp framing modes are not affected. (CVE-2026-19654)

  - Rsyslog is a rocket-fast system for log processing. From 8.2110.0 until 8.2604.0, the optional imhttp
    module's parse_auth_header function in contrib/imhttp/imhttp.c allocates a zero-byte heap buffer with
    calloc(0, len) when an HTTP Basic Authorization value exceeds its fixed work buffer, then passes that
    pointer to apr_base64_decode. An unauthenticated remote attacker can send an oversized encoded credential
    to an imhttp endpoint configured for Basic Authentication, causing decoded data to overwrite adjacent heap
    memory before credential validation. Deployments that do not install, load, and use imhttp with Basic
    Authentication are not affected. The demonstrated impact is a process crash that interrupts log
    collection, and code execution has not been demonstrated. This issue is fixed in version 8.2604.0.
    (CVE-2026-55556)

  - Rsyslog is a rocket-fast system for log processing. From 7.5.4 until 8.2606.0, the optional mmpstrucdata
    plugin's parseSD_PARAM function in plugins/mmpstrucdata/mmpstrucdata.c stores RFC5424 parameter values in
    a fixed pVal[32 * 1024] stack buffer and calls parsePARAM_VALUE without supplying the destination size. A
    remote unauthenticated attacker whose crafted RFC5424 message reaches an action using mmpstrucdata can
    provide a structured-data parameter larger than that buffer when MaxMessageSize permits it, causing an
    attacker-controlled stack overwrite. Deployments that do not install and use the plugin, or whose
    effective message-size limit remains below the required threshold, are not affected by this issue. The
    demonstrated impact is a crash and interruption of log collection; code execution is not demonstrated.
    This issue is fixed in version 8.2606.0. (CVE-2026-61548)

  - A flaw was found in rsyslog. An unauthenticated remote attacker can trigger a heap buffer overflow in the
    RainerScript `replace()` function by sending specially crafted syslog messages. This vulnerability arises
    from an incorrect buffer size calculation during string replacement, causing memory corruption. Successful
    exploitation can lead to a denial of service (DoS) for the affected system. (CVE-2026-78002)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - Debian Linux - rsyslog - None  Ubuntu Linux - [Stack-based Buffer Overflow in mmpstrucdata rsyslog plugin]     (CVE-2026-93403)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
378789	Debian dla-4891 : rsyslog - security update	Nessus	Debian Local Security Checks	Local	high
478598	Alpine: multiple rsyslog packages: security update to 8.2608.0-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	high
478598	Alpine: multiple rsyslog packages: security update to 8.2608.0-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	high
349506	Linux Distros Unpatched Vulnerability : CVE-2026-93403	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-93403

critical

Tenable Plugins

high

high

high

high