{"id":"UBUNTU-CVE-2016-9938","details":"An issue was discovered in Asterisk Open Source 11.x before 11.25.1, 13.x before 13.13.1, and 14.x before 14.2.1 and Certified Asterisk 11.x before 11.6-cert16 and 13.x before 13.8-cert4. The chan_sip channel driver has a liberal definition for whitespace when attempting to strip the content between a SIP header name and a colon character. Rather than following RFC 3261 and stripping only spaces and horizontal tabs, Asterisk treats any non-printable ASCII character as if it were whitespace. This means that headers such as Contact\\x01: will be seen as a valid Contact header. This mostly does not pose a problem until Asterisk is placed in tandem with an authenticating SIP proxy. In such a case, a crafty combination of valid and invalid To headers can cause a proxy to allow an INVITE request into Asterisk without authentication since it believes the request is an in-dialog request. However, because of the bug described above, the request will look like an out-of-dialog request to Asterisk. Asterisk will then process the request as a new call. The result is that Asterisk can process calls from unvetted sources without any authentication. If you do not use a proxy for authentication, then this issue does not affect you. If your proxy is dialog-aware (meaning that the proxy keeps track of what dialogs are currently valid), then this issue does not affect you. If you use chan_pjsip instead of chan_sip, then this issue does not affect you.","modified":"2026-04-22T11:08:00.508002Z","published":"2016-12-12T21:59:00Z","upstream":["CVE-2016-9938"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2016-9938"},{"type":"REPORT","url":"http://downloads.asterisk.org/pub/security/AST-2016-009.html"},{"type":"REPORT","url":"https://issues.asterisk.org/jira/browse/ASTERISK-26433"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2016-9938"}],"affected":[{"package":{"name":"asterisk","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/asterisk@1:13.1.0~dfsg-1.1ubuntu4.1+esm1?arch=source&distro=esm-apps/xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1:13.1.0~dfsg-1.1ubuntu3","1:13.1.0~dfsg-1.1ubuntu4","1:13.1.0~dfsg-1.1ubuntu4.1","1:13.1.0~dfsg-1.1ubuntu4.1+esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"asterisk","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-config","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-dahdi","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-mobile","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-modules","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-mp3","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-mysql","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-ooh323","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-voicemail","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-voicemail-imapstorage","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-voicemail-odbcstorage","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"},{"binary_name":"asterisk-vpb","binary_version":"1:13.1.0~dfsg-1.1ubuntu4.1+esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2016/UBUNTU-CVE-2016-9938.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},{"type":"Ubuntu","score":"low"}]}