{"id":"CVE-2019-11479","published":"2019-06-18T23:34:51Z","modified":"2024-09-16T23:22:00Z","title":"Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes","vendor":"Linux","product":"Linux kernel","tier":"core","eol":null,"affectedVersions":[{"vendor":"Linux","product":"Linux kernel","versions":[">= 4.4, < 4.4.182",">= 4.9, < 4.9.182",">= 4.14, < 4.14.127",">= 4.19, < 4.19.52",">= 5.1, < 5.1.11"]}],"description":{"text":"Jonathan Looney discovered that the Linux kernel default MSS is hard-coded to 48 bytes. This allows a remote peer to fragment TCP resend queues significantly more than if a larger MSS were enforced. A remote attacker could use this to cause a denial of service. This has been fixed in stable kernel releases 4.4.182, 4.9.182, 4.14.127, 4.19.52, 5.1.11, and is fixed in commits 967c05aee439e6e5d7d805e195b3a20ef5c433d6 and 5f3e2bf008c2221478101ee72f5cb4654b9fc363.","provenance":"source","from":"CVE.org"},"summary":{"text":"The Linux kernel's TCP stack hard-codes its default maximum segment size (MSS) to 48 bytes, which causes TCP resend queues to be fragmented far more than a larger enforced MSS would. A remote peer with network access can exploit this without authentication or user interaction to cause a denial of service.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-29T07:22:24Z"},"cvss":{"score":5.3,"severity":"MEDIUM","version":"3.0","vector":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","provenance":"source","from":"CVE.org CNA"},"epss":{"score":0.9166,"percentile":0.99813,"date":"2026-10-28","provenance":"source"},"kev":null,"vulncheckKev":null,"exploited":false,"otx":{"pulseCount":1,"pulses":[{"name":"Denial-of-service attack - Wikipedia","url":"https://otx.alienvault.com/pulse/62a0bf6f19bd1b5809dfb760","created":"2022-06-08"}],"provenance":"machine"},"cwes":[{"id":"CWE-405","name":"Asymmetric Resource Consumption (Amplification)"}],"references":[{"url":"http://www.securityfocus.com/bid/108818","tags":["vdb-entry","x_refsource_BID"]},{"url":"https://www.kb.cert.org/vuls/id/905115","tags":["third-party-advisory","x_refsource_CERT-VN"]},{"url":"https://access.redhat.com/errata/RHSA-2019:1594","tags":["vendor-advisory","x_refsource_REDHAT"]},{"url":"https://access.redhat.com/errata/RHSA-2019:1602","tags":["vendor-advisory","x_refsource_REDHAT"]},{"url":"http://www.openwall.com/lists/oss-security/2019/06/28/2","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://usn.ubuntu.com/4041-2/","tags":["vendor-advisory","x_refsource_UBUNTU"]},{"url":"http://www.openwall.com/lists/oss-security/2019/07/06/3","tags":["mailing-list","x_refsource_MLIST"]},{"url":"http://www.openwall.com/lists/oss-security/2019/07/06/4","tags":["mailing-list","x_refsource_MLIST"]},{"url":"https://access.redhat.com/errata/RHSA-2019:1699","tags":["vendor-advisory","x_refsource_REDHAT"]},{"url":"https://usn.ubuntu.com/4041-1/","tags":["vendor-advisory","x_refsource_UBUNTU"]},{"url":"https://www.oracle.com/security-alerts/cpujan2020.html","tags":["x_refsource_MISC"]},{"url":"https://www.oracle.com/security-alerts/cpuoct2020.html","tags":["x_refsource_MISC"]},{"url":"https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-001.md","tags":["x_refsource_MISC"]},{"url":"https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/SACKPanic","tags":["x_refsource_MISC"]},{"url":"https://access.redhat.com/security/vulnerabilities/tcpsack","tags":["x_refsource_MISC"]},{"url":"https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44193","tags":["x_refsource_CONFIRM"]},{"url":"https://www.synology.com/security/advisory/Synology_SA_19_28","tags":["x_refsource_CONFIRM"]},{"url":"https://security.netapp.com/advisory/ntap-20190625-0001/","tags":["x_refsource_CONFIRM"]},{"url":"https://kc.mcafee.com/corporate/index?page=content&id=SB10287","tags":["x_refsource_CONFIRM"]},{"url":"https://cert-portal.siemens.com/productcert/pdf/ssa-462066.pdf","tags":["x_refsource_CONFIRM"]},{"url":"https://www.us-cert.gov/ics/advisories/icsa-19-253-03","tags":["x_refsource_MISC"]},{"url":"http://www.arubanetworks.com/assets/alert/ARUBA-PSA-2020-010.txt","tags":["x_refsource_CONFIRM"]},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=5f3e2bf008c2221478101ee72f5cb4654b9fc363","tags":["x_refsource_MISC"]},{"url":"https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=967c05aee439e6e5d7d805e195b3a20ef5c433d6","tags":["x_refsource_MISC"]},{"url":"https://support.f5.com/csp/article/K35421172","tags":["x_refsource_CONFIRM"]},{"url":"https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2019-0008","tags":["x_refsource_CONFIRM"]},{"url":"https://support.f5.com/csp/article/K35421172?utm_source=f5support&amp%3Butm_medium=RSS","tags":["x_refsource_CONFIRM"]},{"url":"https://www.us-cert.gov/ics/advisories/icsma-20-170-06","tags":["x_refsource_MISC"]}],"techniques":[],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2019-3152","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2019-3152","exploited":false,"exploitedSince":null,"provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[],"timeline":[{"date":"2019-06-18","kind":"published","label":"Published (CVE.org)","url":"https://www.cve.org/CVERecord?id=CVE-2019-11479","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":null},"priority":{"score":24.4,"factors":[{"name":"In a KEV catalog","points":0.0,"detail":"not listed"},{"name":"Recent KEV listing","points":0.0,"detail":"not listed"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.96,"detail":"percentile 0.9981"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":0.0,"detail":"none found"},{"name":"Mentioned in OTX pulses","points":0.68,"detail":"1 pulse"},{"name":"CVSS severity","points":3.71,"detail":"base score 5.3"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}