An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6. When re-negotiating for T.38, if the initial remote response was delayed just enough, Asterisk would send both audio and T.38 in the SDP. If this happened, and the remote responded with a declined T.38 stream, then Asterisk would crash.

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

  - An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x before     18.2.1 and Certified Asterisk before 16.8-cert6. When re-negotiating for T.38, if the initial remote     response was delayed just enough, Asterisk would send both audio and T.38 in the SDP. If this happened,     and the remote responded with a declined T.38 stream, then Asterisk would crash. (CVE-2021-26717)

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

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

  - Incorrect access controls in res_srtp.c in Sangoma Asterisk 13.38.1, 16.16.0, 17.9.1, and 18.2.0 and
    Certified Asterisk 16.8-cert5 allow a remote unauthenticated attacker to prematurely terminate secure
    calls by replaying SRTP packets. (CVE-2021-26712)

  - A stack-based buffer overflow in res_rtp_asterisk.c in Sangoma Asterisk before 16.16.1, 17.x before
    17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6 allows an authenticated WebRTC
    client to cause an Asterisk crash by sending multiple hold/unhold requests in quick succession. This is
    caused by a signedness comparison mismatch. (CVE-2021-26713)

  - An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x before
    18.2.1 and Certified Asterisk before 16.8-cert6. When re-negotiating for T.38, if the initial remote
    response was delayed just enough, Asterisk would send both audio and T.38 in the SDP. If this happened,
    and the remote responded with a declined T.38 stream, then Asterisk would crash. (CVE-2021-26717)

  - An issue was discovered in res_pjsip_session.c in Digium Asterisk through 13.38.1; 14.x, 15.x, and 16.x
    through 16.16.0; 17.x through 17.9.1; and 18.x through 18.2.0, and Certified Asterisk through 16.8-cert5.
    An SDP negotiation vulnerability in PJSIP allows a remote server to potentially crash Asterisk by sending
    specific SIP responses that cause an SDP negotiation failure. (CVE-2021-26906)

The remote host is affected by the vulnerability described in GLSA-202412-03 (Asterisk: Multiple Vulnerabilities)

    Multiple vulnerabilities have been discovered in Asterisk. Please review the CVE identifiers referenced     below for details.

Tenable has extracted the preceding description block directly from the Gentoo Linux 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 buffer overflow in res_pjsip_diversion.c in Sangoma Asterisk versions 13.38.1, 16.15.1, 17.9.1, and
    18.1.1 allows remote attacker to crash Asterisk by deliberately misusing SIP 181 responses.
    (CVE-2020-35776)

  - Incorrect access controls in res_srtp.c in Sangoma Asterisk 13.38.1, 16.16.0, 17.9.1, and 18.2.0 and
    Certified Asterisk 16.8-cert5 allow a remote unauthenticated attacker to prematurely terminate secure
    calls by replaying SRTP packets. (CVE-2021-26712)

  - A stack-based buffer overflow in res_rtp_asterisk.c in Sangoma Asterisk before 16.16.1, 17.x before
    17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6 allows an authenticated WebRTC
    client to cause an Asterisk crash by sending multiple hold/unhold requests in quick succession. This is
    caused by a signedness comparison mismatch. (CVE-2021-26713)

  - An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x before
    18.2.1 and Certified Asterisk before 16.8-cert6. When re-negotiating for T.38, if the initial remote
    response was delayed just enough, Asterisk would send both audio and T.38 in the SDP. If this happened,
    and the remote responded with a declined T.38 stream, then Asterisk would crash. (CVE-2021-26717)

  - An issue was discovered in res_pjsip_session.c in Digium Asterisk through 13.38.1; 14.x, 15.x, and 16.x
    through 16.16.0; 17.x through 17.9.1; and 18.x through 18.2.0, and Certified Asterisk through 16.8-cert5.
    An SDP negotiation vulnerability in PJSIP allows a remote server to potentially crash Asterisk by sending
    specific SIP responses that cause an SDP negotiation failure. (CVE-2021-26906)

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

  - An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x before
    18.2.1 and Certified Asterisk before 16.8-cert6. When re-negotiating for T.38, if the initial remote
    response was delayed just enough, Asterisk would send both audio and T.38 in the SDP. If this happened,
    and the remote responded with a declined T.38 stream, then Asterisk would crash. (CVE-2021-26717)

  - A res_pjsip_session crash was discovered in Asterisk Open Source 13.x before 13.37.1, 16.x before 16.14.1,
    17.x before 17.8.1, and 18.x before 18.0.1. and Certified Asterisk before 16.8-cert5. Upon receiving a new
    SIP Invite, Asterisk did not return the created dialog locked or referenced. This caused a gap between the
    creation of the dialog object, and its next use by the thread that created it. Depending on some off-
    nominal circumstances and timing, it was possible for another thread to free said dialog in this gap.
    Asterisk could then crash when the dialog object, or any of its dependent objects, were dereferenced or
    accessed next by the initial-creation thread. Note, however, that this crash can only occur when using a
    connection-oriented protocol (e.g., TCP or TLS, but not UDP) for SIP transport. Also, the remote client
    must be authenticated, or Asterisk must be configured for anonymous calling. (CVE-2020-28327)

  - An issue was discovered in res_pjsip_diversion.c in Sangoma Asterisk before 13.38.0, 14.x through 16.x
    before 16.15.0, 17.x before 17.9.0, and 18.x before 18.1.0. A crash can occur when a SIP message is
    received with a History-Info header that contains a tel-uri, or when a SIP 181 response is received that
    contains a tel-uri in the Diversion header. (CVE-2020-35652)

  - A buffer overflow in res_pjsip_diversion.c in Sangoma Asterisk versions 13.38.1, 16.15.1, 17.9.1, and
    18.1.1 allows remote attacker to crash Asterisk by deliberately misusing SIP 181 responses.
    (CVE-2020-35776)

  - Incorrect access controls in res_srtp.c in Sangoma Asterisk 13.38.1, 16.16.0, 17.9.1, and 18.2.0 and
    Certified Asterisk 16.8-cert5 allow a remote unauthenticated attacker to prematurely terminate secure
    calls by replaying SRTP packets. (CVE-2021-26712)

The Asterisk project reports :

When re-negotiating for T.38 if the initial remote response was delayed just enough Asterisk would send both audio and T.38 in the SDP. If this happened, and the remote responded with a declined T.38 stream then Asterisk would crash.

ID	Name	Product	Family	Severity
252364	Linux Distros Unpatched Vulnerability : CVE-2021-26717	Nessus	Misc.	high
423684	Alpine: multiple asterisk packages: security update to 18.2.1-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	high
423684	Alpine: multiple asterisk packages: security update to 18.2.1-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	high
212188	GLSA-202412-03 : Asterisk: Multiple Vulnerabilities	Nessus	Gentoo Local Security Checks	critical
403580	Alpine: asterisk: security update to 16.16.1-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	high
403580	Alpine: asterisk: security update to 16.16.1-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	high
400268	Alpine: multiple asterisk packages: security update to 18.1.1-r0 (deprecated)	Tenable Cloud Security	Alpine Linux Local Security Checks	high
400268	Alpine: multiple asterisk packages: security update to 18.1.1-r0 (deprecated)	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	high
146616	FreeBSD : asterisk -- Remote crash possible when negotiating T.38 (e3894955-7227-11eb-8386-001999f8d30b)	Nessus	FreeBSD Local Security Checks	high

Detections

Analytics

CVE-2021-26717

high

Tenable Plugins

high

high

high

critical

high

high

high

high

high