{"id":"CVE-2026-31503","title":"kernel: udp: Fix wildcard bind conflict check when using hash2 (CVE-2026-31503)","summary":"A flaw was found in the Linux kernel's User Datagram Protocol (UDP) implementation. When a significant number of UDP sockets are bound to specific local addresses on the same port, the kernel's conflict detection mechanism can fail. This a…","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","cvssSource":"vendor","cwe":"CWE-253","vendor":"Red Hat","product":"Red Hat Enterprise Linux BaseOS (v. 10)","affected":["enterprise_linux 6","enterprise_linux 7","enterprise_linux 8","enterprise_linux 9","enterprise_linux_appstream_v_10","enterprise_linux_baseos_v_10","enterprise_linux_codeready_linux_builder_v_10","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_real_time_v_10"],"patched":["enterprise_linux_appstream_v_10","enterprise_linux_baseos_v_10","enterprise_linux_codeready_linux_builder_v_10","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_real_time_v_10"],"published":"2026-04-22","updated":"2026-09-08","sourceUpdated":"2026-09-08T22:29:18+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31503.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31503.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-31503"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2460736"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-31503"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31503"},{"url":"https://lore.kernel.org/linux-cve-announce/2026042206-CVE-2026-31503-602a@gregkh/T"},{"url":"https://access.redhat.com/errata/RHSA-2026:64775"},{"url":"https://git.kernel.org/stable/c/d6ace0dbcbb7fd285738bb87b42b71b01858c952"},{"url":"https://git.kernel.org/stable/c/2297e38114316b26ae02f2d205c49b5511c5ed55"},{"url":"https://git.kernel.org/stable/c/f1bed05a832ae79be5f7a105da56810eaa59a5f1"},{"url":"https://git.kernel.org/stable/c/18d84c45def3671d5c89fbdd5d4ab8a3217fe4b4"},{"url":"https://git.kernel.org/stable/c/0a360f7f73a06ac88f18917055fbcc79694252d7"},{"url":"https://git.kernel.org/stable/c/e537dd15d0d4ad989d56a1021290f0c674dd8b28"}],"tags":["csaf","vex","red-hat","cve.org"],"epss":0.00123,"epssPercentile":0.02361,"ingestedAt":"2026-09-08T15:33:26.990Z","slug":"CVE-2026-31503","body":"## Overview\n\nA flaw was found in the Linux kernel's User Datagram Protocol (UDP) implementation. When a significant number of UDP sockets are bound to specific local addresses on the same port, the kernel's conflict detection mechanism can fail. This allows a local attacker to bind to a wildcard address on a port that should already be in use, potentially leading to a Denial of Service (DoS) for legitimate applications attempting to use that port.\n\n## Vendor advisories\n\n- **RHSA-2026:64775** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), Red Hat Enterprise Linux Real Time (v. 10) · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:64775)\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · updated 2026-09-08 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-31503.json)\n\n**kernel: udp: Fix wildcard bind conflict check when using hash2** — rated Moderate by Red Hat. Released 2026-04-22, updated 2026-09-08.\n\nAffected:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\n- Red Hat Enterprise Linux 8\n- Red Hat Enterprise Linux 9\n\nFixed:\n\n- Red Hat Enterprise Linux AppStream (v. 10)\n- Red Hat Enterprise Linux BaseOS (v. 10)\n- Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)\n- Red Hat Enterprise Linux Real Time for NFV (v. 10)\n- Red Hat Enterprise Linux Real Time (v. 10)\n\nNo fix planned:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\n- Red Hat Enterprise Linux 8\n- Red Hat Enterprise Linux 9\n\n## Remediation\n\nFor details on how to apply this update, which includes the changes described in this advisory, refer to:\n\nhttps://access.redhat.com/articles/11258\n\nThe system must be rebooted for this update to take effect.\n\nRed Hat recommends treating all kernel errata as security-relevant. Given the kernel's fundamental role, any bug has a higher chance of impacting system security, even if that impact only becomes clear after a fix is published. Therefore, Red Hat prioritizes delivering fixes that improve our customers' overall security posture.\n\nBecause of this proactive approach, a patch may be associa… https://access.redhat.com/errata/RHSA-2026:64775\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 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