{"id":"CVE-2025-37913","title":"kernel: net_sched: qfq: Fix double list add in class with netem as child qdisc (CVE-2025-37913)","summary":"A flaw was found in the Linux kernel's Quick Fair Queueing (QFQ) network traffic scheduler. When nested queuing disciplines trigger reentrant packet enqueue operations, the scheduler fails to verify whether a class is already active before…","severity":"medium","cvss":6.3,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H","cvssSource":"vendor","cwe":"CWE-367","vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","affected":["enterprise_linux 6","enterprise_linux 7","enterprise_linux 8"],"published":"2025-05-20","updated":"2026-10-16","sourceUpdated":"2026-10-16T22:55:33+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37913.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37913.json"},{"url":"https://access.redhat.com/security/cve/CVE-2025-37913"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2367518"},{"url":"https://www.cve.org/CVERecord?id=CVE-2025-37913"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-37913"},{"url":"https://lore.kernel.org/linux-cve-announce/2025052000-CVE-2025-37913-95be@gregkh/T"},{"url":"https://git.kernel.org/stable/c/041f410aec2c1751ee22b8b73ba05d38c3a6a602"},{"url":"https://git.kernel.org/stable/c/005a479540478a820c52de098e5e767e63e36f0a"},{"url":"https://git.kernel.org/stable/c/0bf32d6fb1fcbf841bb9945570e0e2a70072c00f"},{"url":"https://git.kernel.org/stable/c/0aa23e0856b7cedb3c88d8e3d281c212c7e4fbeb"},{"url":"https://git.kernel.org/stable/c/a43783119e01849fbf2fe8855634e8989b240cb4"},{"url":"https://git.kernel.org/stable/c/53bc0b55178bd59bdd4bcd16349505cabf54b1a2"},{"url":"https://git.kernel.org/stable/c/370218e8ce711684acc4cdd3cc3c6dd7956bc165"},{"url":"https://git.kernel.org/stable/c/f139f37dcdf34b67f5bf92bc8e0f7f6b3ac63aa4"}],"tags":["csaf","vex","red-hat","cve.org"],"epss":0.00237,"epssPercentile":0.13748,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-15T21:45:52.578125Z"},"scores":{"vendor":6.3,"cna":7.8},"ingestedAt":"2026-10-15T22:48:25.482Z","slug":"CVE-2025-37913","body":"## Overview\n\nA flaw was found in the Linux kernel's Quick Fair Queueing (QFQ) network traffic scheduler. When nested queuing disciplines trigger reentrant packet enqueue operations, the scheduler fails to verify whether a class is already active before adding it, resulting in duplicate list insertion. A local user could exploit this flaw to cause memory corruption, leading to a system crash and Denial of Service (DoS).\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8 · updated 2026-10-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-37913.json)\n\n**kernel: net_sched: qfq: Fix double list add in class with netem as child qdisc** — rated Moderate by Red Hat. Released 2025-05-20, updated 2026-10-16.\n\nAffected:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\n- Red Hat Enterprise Linux 8\n\nNo fix planned:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\n- Red Hat Enterprise Linux 8\n\nNot affected:\n\n- Red Hat Enterprise Linux 10\n- Red Hat Enterprise Linux 9\n\n## Remediation\n\nOut of support scope\n\nWorkarounds / mitigations:\n\n- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.","depth":"sunlit","depthScore":35,"depthScoreParts":{"impact":34.7,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":223733,"id":"CVE-2025-37913","ts":1792238379489,"field":"cvss","old":"7.8","new":"6.3"},{"seq":223732,"id":"CVE-2025-37913","ts":1792238379489,"field":"severity","old":"high","new":"medium"}]}