{"id":"CVE-2026-63920","title":"kernel: ipv6: validate extension header length before copying to cmsg (CVE-2026-63920)","summary":"A flaw was found in the Linux kernel's IPv6 networking stack. An unprivileged local user could exploit a vulnerability in how IPv6 extension header lengths are handled. By manipulating these headers using nftables, an attacker can trigger …","severity":"high","cvss":7,"cvssVector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"vendor","cwe":"CWE-125","vendor":"Red Hat","product":"Red Hat Enterprise Linux BaseOS E4S (v.9.4)","affected":["enterprise_linux 6","enterprise_linux 7","enterprise_linux 9","10base_smtv","enterprise_linux_appstream_eus_v_10_0","enterprise_linux_appstream_v_10","enterprise_linux_appstream_e4s_v_9_4","enterprise_linux_appstream_eus_v_9_6","enterprise_linux_appstream_v_9","enterprise_linux_baseos_eus_v_10_0","enterprise_linux_baseos_v_10","enterprise_linux_baseos_v_8","enterprise_linux_baseos_aus_v_8_4","enterprise_linux_baseos_eus_extension_v_8_4","enterprise_linux_baseos_aus_v_8_6","enterprise_linux_baseos_eus_extension_v_8_6","enterprise_linux_baseos_e4s_v_8_8","enterprise_linux_baseos_tus_v_8_8","enterprise_linux_baseos_e4s_v_9_4","enterprise_linux_baseos_eus_v_9_6","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_eus_v_10_0","enterprise_linux_codeready_linux_builder_v_10","enterprise_linux_crb_v_8","codeready_linux_builder_eus_v_9_6","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_hidden_v_10","enterprise_linux_real_time_for_nfv_eus_v_10_0","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_nfv_v_8","enterprise_linux_real_time_for_nfv_e4s_v_9_4","enterprise_linux_real_time_for_nfv_eus_v_9_6","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_eus_v_10_0","enterprise_linux_real_time_v_10","enterprise_linux_rt_v_8","enterprise_linux_real_time_e4s_v_9_4","enterprise_linux_real_time_eus_v_9_6","enterprise_linux_real_time_v_9"],"patched":["10base_smtv","enterprise_linux_appstream_eus_v_10_0","enterprise_linux_appstream_v_10","enterprise_linux_appstream_e4s_v_9_4","enterprise_linux_appstream_eus_v_9_6","enterprise_linux_appstream_v_9","enterprise_linux_baseos_eus_v_10_0","enterprise_linux_baseos_v_10","enterprise_linux_baseos_v_8","enterprise_linux_baseos_aus_v_8_4","enterprise_linux_baseos_eus_extension_v_8_4","enterprise_linux_baseos_aus_v_8_6","enterprise_linux_baseos_eus_extension_v_8_6","enterprise_linux_baseos_e4s_v_8_8","enterprise_linux_baseos_tus_v_8_8","enterprise_linux_baseos_e4s_v_9_4","enterprise_linux_baseos_eus_v_9_6","enterprise_linux_baseos_v_9","enterprise_linux_codeready_linux_builder_eus_v_10_0","enterprise_linux_codeready_linux_builder_v_10","enterprise_linux_crb_v_8","codeready_linux_builder_eus_v_9_6","enterprise_linux_codeready_linux_builder_v_9","enterprise_linux_hidden_v_10","enterprise_linux_real_time_for_nfv_eus_v_10_0","enterprise_linux_real_time_for_nfv_v_10","enterprise_linux_nfv_v_8","enterprise_linux_real_time_for_nfv_e4s_v_9_4","enterprise_linux_real_time_for_nfv_eus_v_9_6","enterprise_linux_real_time_for_nfv_v_9","enterprise_linux_real_time_eus_v_10_0","enterprise_linux_real_time_v_10","enterprise_linux_rt_v_8","enterprise_linux_real_time_e4s_v_9_4","enterprise_linux_real_time_eus_v_9_6","enterprise_linux_real_time_v_9"],"published":"2026-07-19","updated":"2026-10-26","sourceUpdated":"2026-10-26T09:37:30+00:00","source":"CSAF","sourceUrl":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63920.json","references":[{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63920.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-63920"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2502330"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-63920"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63920"},{"url":"https://lore.kernel.org/linux-cve-announce/2026071948-CVE-2026-63920-54a7@gregkh/T"},{"url":"https://access.redhat.com/errata/RHSA-2026:76738"},{"url":"https://access.redhat.com/errata/RHSA-2026:83707"},{"url":"https://access.redhat.com/errata/RHSA-2026:77218"},{"url":"https://access.redhat.com/errata/RHSA-2026:77219"},{"url":"https://access.redhat.com/errata/RHSA-2026:76739"},{"url":"https://access.redhat.com/errata/RHSA-2026:82807"},{"url":"https://access.redhat.com/errata/RHSA-2026:84677"},{"url":"https://access.redhat.com/errata/RHSA-2026:85000"},{"url":"https://access.redhat.com/errata/RHSA-2026:84793"},{"url":"https://access.redhat.com/errata/RHSA-2026:82806"},{"url":"https://git.kernel.org/stable/c/81394827dfb72772c50d0ae3bdfa094428a5d76d"},{"url":"https://git.kernel.org/stable/c/931b4a1f13408c2507719890f78f7227c34a0282"},{"url":"https://git.kernel.org/stable/c/08464413e628803bd10cb1df68d0138665f2f885"},{"url":"https://git.kernel.org/stable/c/a29768d56eb3798c052ad3281b05596e695a17af"},{"url":"https://git.kernel.org/stable/c/0d330eff318c0f44d4fb0ad2c2aef38f87f24c90"},{"url":"https://git.kernel.org/stable/c/a35daeabb433686234b010ebf7b53778dbd6c9b8"},{"url":"https://git.kernel.org/stable/c/eb18a1b1644e4cad978df2131e2bb9a2e6886992"},{"url":"https://git.kernel.org/stable/c/dd433671fef381fdaf7b530c631e6b782d66e224"}],"tags":["csaf","vex","red-hat","cve.org"],"epss":0.00172,"epssPercentile":0.06522,"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"partial","timestamp":"2026-10-16T15:33:23.448048Z"},"scores":{"vendor":7,"cna":7.1},"ingestedAt":"2026-10-16T17:24:46.775Z","slug":"CVE-2026-63920","body":"## Overview\n\nA flaw was found in the Linux kernel's IPv6 networking stack. An unprivileged local user could exploit a vulnerability in how IPv6 extension header lengths are handled. By manipulating these headers using nftables, an attacker can trigger an out-of-bounds read, leading to information disclosure from kernel memory.\n\n## Vendor advisories\n\n- **RHSA-2026:76738** · Red Hat · fixed in: 10Base-SMTV, 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 Hidden (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), … · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:76738)\n- **RHSA-2026:83707** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0), Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0), Red Hat Enterprise Linux Real Time EUS (v. 10.0) · released 2026-10-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:83707)\n- **RHSA-2026:77218** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream E4S (v.9.4), Red Hat Enterprise Linux BaseOS E4S (v.9.4), Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4), Red Hat Enterprise Linux Real Time E4S (v.9.4) · released 2026-10-07 · [advisory](https://access.redhat.com/errata/RHSA-2026:77218)\n- **RHSA-2026:77219** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6), Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6), Red Hat Enterprise Linux Real Time EUS (v.9.6) · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:77219)\n- **RHSA-2026:76739** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:76739)\n- **RHSA-2026:82807** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8) · released 2026-10-14 · [advisory](https://access.redhat.com/errata/RHSA-2026:82807)\n- **RHSA-2026:84677** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS AUS (v.8.4), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84677)\n- **RHSA-2026:85000** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS AUS (v.8.6), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:85000)\n- **RHSA-2026:84793** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS E4S (v.8.8), Red Hat Enterprise Linux BaseOS TUS (v.8.8) · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84793)\n- **RHSA-2026:82806** · Red Hat · fixed in: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8) · released 2026-10-14 · [advisory](https://access.redhat.com/errata/RHSA-2026:82806)\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 9 · updated 2026-10-26 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63920.json)\n\n**kernel: ipv6: validate extension header length before copying to cmsg** — rated Moderate by Red Hat. Released 2026-07-19, updated 2026-10-26.\n\nAffected:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\n- Red Hat Enterprise Linux 9\n\nFixed:\n\n- 10Base-SMTV\n- Red Hat Enterprise Linux AppStream EUS (v. 10.0)\n- Red Hat Enterprise Linux AppStream (v. 10)\n- Red Hat Enterprise Linux AppStream E4S (v.9.4)\n- Red Hat Enterprise Linux AppStream EUS (v.9.6)\n- Red Hat Enterprise Linux AppStream (v. 9)\n- Red Hat Enterprise Linux BaseOS EUS (v. 10.0)\n- Red Hat Enterprise Linux BaseOS (v. 10)\n- Red Hat Enterprise Linux BaseOS (v. 8)\n- Red Hat Enterprise Linux BaseOS AUS (v.8.4)\n- Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)\n- Red Hat Enterprise Linux BaseOS AUS (v.8.6)\n- Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6)\n- Red Hat Enterprise Linux BaseOS E4S (v.8.8)\n- Red Hat Enterprise Linux BaseOS TUS (v.8.8)\n- Red Hat Enterprise Linux BaseOS E4S (v.9.4)\n- Red Hat Enterprise Linux BaseOS EUS (v.9.6)\n- Red Hat Enterprise Linux BaseOS (v. 9)\n- Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)\n- Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)\n- Red Hat Enterprise Linux CRB (v. 8)\n- Red Hat CodeReady Linux Builder EUS (v.9.6)\n- Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)\n- Red Hat Enterprise Linux Hidden (v. 10)\n- Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0)\n- Red Hat Enterprise Linux Real Time for NFV (v. 10)\n- Red Hat Enterprise Linux NFV (v. 8)\n- Red Hat Enterprise Linux Real Time for NFV E4S (v.9.4)\n- Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6)\n- Red Hat Enterprise Linux Real Time for NFV (v. 9)\n- Red Hat Enterprise Linux Real Time EUS (v. 10.0)\n- Red Hat Enterprise Linux Real Time (v. 10)\n- Red Hat Enterprise Linux RT (v. 8)\n- Red Hat Enterprise Linux Real Time E4S (v.9.4)\n- Red Hat Enterprise Linux Real Time EUS (v.9.6)\n- Red Hat Enterprise Linux Real Time (v. 9)\n\nNo fix planned:\n\n- Red Hat Enterprise Linux 6\n- Red Hat Enterprise Linux 7\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-2026:76738\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-2026:83707\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-2026:77218","depth":"twilight","depthScore":39,"depthScoreParts":{"impact":38.5,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":229343,"id":"CVE-2026-63920","ts":1793019697603,"field":"cvss","old":"7.1","new":"7"},{"seq":225202,"id":"CVE-2026-63920","ts":1792442542877,"field":"cvss","old":"7","new":"7.1"},{"seq":223805,"id":"CVE-2026-63920","ts":1792238435510,"field":"cvss","old":"7.1","new":"7"}]}