--- id: CVE-2018-14647 title: >- Python's elementtree C accelerator failed to initialise Expat's hash salt during initialization summary: >- Python's elementtree C accelerator failed to initialise Expat's hash salt during initialization. This could make it easy to conduct denial of service attacks against Expat by constructing an XML document that would cause pathological has… severity: high cvss: 7.5 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H' cwe: - CWE-335 - CWE-665 - CWE-909 vendor: python product: python affected: - 'python >= 2.7.0, <= 2.7.15' - 'python >= 3.4.0, <= 3.4.9' - 'python >= 3.5.0, <= 3.5.6' - 'python >= 3.6.0, <= 3.6.6' - python = 3.7.0 - ubuntu_linux = 12.04 - ubuntu_linux = 14.04 - ubuntu_linux = 16.04 - ubuntu_linux = 18.04 - debian_linux = 8.0 - debian_linux = 9.0 - fedora = 30 - leap = 15.1 - enterprise_linux_desktop = 7.0 - enterprise_linux_server = 7.0 - enterprise_linux_workstation = 7.0 published: '2018-09-25' updated: '2026-10-07' sourceUpdated: '2026-10-07T19:17:11.210' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2018-14647' references: - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00040.html' label: secalert@redhat.com - url: 'http://www.securityfocus.com/bid/105396' label: secalert@redhat.com - url: 'http://www.securitytracker.com/id/1041740' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2019:1260' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2019:2030' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2019:3725' label: secalert@redhat.com - url: 'https://bugs.python.org/issue34623' label: secalert@redhat.com - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-14647' label: secalert@redhat.com - url: >- https://lists.apache.org/thread.html/r1b103833cb5bc8466e24ff0ecc5e75b45a705334ab6a444e64e840a0%40%3Cissues.bookkeeper.apache.org%3E label: secalert@redhat.com - url: 'https://lists.debian.org/debian-lts-announce/2019/06/msg00022.html' label: secalert@redhat.com - url: 'https://lists.debian.org/debian-lts-announce/2019/06/msg00023.html' label: secalert@redhat.com - url: >- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RBJCB2HWOJLP3L7CUQHJHNBHLSVOXJE5/ label: secalert@redhat.com - url: 'https://usn.ubuntu.com/3817-1/' label: secalert@redhat.com - url: 'https://usn.ubuntu.com/3817-2/' label: secalert@redhat.com - url: 'https://www.debian.org/security/2018/dsa-4306' label: secalert@redhat.com - url: 'https://www.debian.org/security/2018/dsa-4307' label: secalert@redhat.com - url: 'http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00040.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'http://www.securityfocus.com/bid/105396' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'http://www.securitytracker.com/id/1041740' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://access.redhat.com/errata/RHSA-2019:1260' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://access.redhat.com/errata/RHSA-2019:2030' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://access.redhat.com/errata/RHSA-2019:3725' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://bugs.python.org/issue34623' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-14647' label: af854a3a-2127-422b-91ae-364da2661108 - url: >- https://lists.apache.org/thread.html/r1b103833cb5bc8466e24ff0ecc5e75b45a705334ab6a444e64e840a0%40%3Cissues.bookkeeper.apache.org%3E label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://lists.debian.org/debian-lts-announce/2019/06/msg00022.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://lists.debian.org/debian-lts-announce/2019/06/msg00023.html' label: af854a3a-2127-422b-91ae-364da2661108 - url: >- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RBJCB2HWOJLP3L7CUQHJHNBHLSVOXJE5/ label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://usn.ubuntu.com/3817-1/' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://usn.ubuntu.com/3817-2/' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://www.debian.org/security/2018/dsa-4306' label: af854a3a-2127-422b-91ae-364da2661108 - url: 'https://www.debian.org/security/2018/dsa-4307' label: af854a3a-2127-422b-91ae-364da2661108 tags: - nvd - cve.org - score-dispute ssvc: exploitation: none automatable: 'no' technicalImpact: partial timestamp: '2026-10-07T18:28:53.788379Z' scores: nvd: 7.5 cna: 5.3 epss: 0.10911 epssPercentile: 0.95765 ingestedAt: '2026-10-07T19:44:15.634Z' --- ## Overview Python's elementtree C accelerator failed to initialise Expat's hash salt during initialization. This could make it easy to conduct denial of service attacks against Expat by constructing an XML document that would cause pathological hash collisions in Expat's internal data structures, consuming large amounts CPU and RAM. The vulnerability exists in Python versions 3.7.0, 3.6.0 through 3.6.6, 3.5.0 through 3.5.6, 3.4.0 through 3.4.9, 2.7.0 through 2.7.15. ## Affected - `python >= 2.7.0, <= 2.7.15` - `python >= 3.4.0, <= 3.4.9` - `python >= 3.5.0, <= 3.5.6` - `python >= 3.6.0, <= 3.6.6` - `python = 3.7.0` - `ubuntu_linux = 12.04` - `ubuntu_linux = 14.04` - `ubuntu_linux = 16.04` - `ubuntu_linux = 18.04` - `debian_linux = 8.0` - `debian_linux = 9.0` - `fedora = 30` - `leap = 15.1` - `enterprise_linux_desktop = 7.0` - `enterprise_linux_server = 7.0` - `enterprise_linux_workstation = 7.0` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges.