# CVE-2026-63827: apparmor: fix use-after-free in rawdata dedup loop CVE-2026-63827 is fixed in 17 products on 1 platform, first by DEBIAN-CVE-2026-63827, released July 20, 2026. It is not reported as exploited. Patch Radar priority: Urgent. - Web page: https://patchblox.com/security/cve/CVE-2026-63827 - Priority: Urgent - CVSS: 9.8 (Critical) - EPSS: 0.0012 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Jul 19, 2026 - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63827 ## Description In the Linux kernel, the following vulnerability has been resolved: apparmor: fix use-after-free in rawdata dedup loop aa_replace_profiles() walks ns->rawdata_list to dedup the incoming policy blob against entries already attached to existing profiles. Per the kernel-doc on struct aa_loaddata, list membership does not hold a reference: profiles hold pcount, and when the last pcount drops, do_ploaddata_rmfs() is queued on a workqueue that takes ns->lock and removes the entry. Between dropping the last pcount and the workqueue running, an entry remains on the list with pcount == 0. aa_get_profile_loaddata() is an unconditional kref_get() on pcount, so when the dedup loop hits such an entry, refcount hardening reports refcount_t: addition on 0; use-after-free. inside aa_replace_profiles(), and the poisoned counter then trips "saturated" and "underflow" warnings on the subsequent uses of the same loaddata. Before commit a0b7091c4de4 ("apparmor: fix race on rawdata dereference") the dedup path used a get_unless_zero-style helper on a single counter, so the existing "if (tmp)" guard was meaningful. The split-refcount refactor introduced aa_get_profile_loaddata(), which has plain kref_get() semantics, and the guard quietly became a no-op. Introduce aa_get_profile_loaddata_not0(), matching the existing _not0 convention used by aa_get_profile_not0(), and use it for the rawdata_list dedup lookup so dying entries are skipped. Reproduced on x86_64 with v7.1-rc5 in QEMU+KVM running Ubuntu 24.04 + stress-ng 0.17.06: stress-ng --apparmor 1 --klog-check --timeout 60s Without this patch the three refcount_t warnings fire within a few seconds. With it the same 60 s run is clean. Coverage is a smoke-test only; a longer soak with CONFIG_KASAN, CONFIG_KCSAN and CONFIG_PROVE_LOCKING would be welcome from anyone with the cycles. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | dtb-aarch64 opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-64kb opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-64kb sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-64kb sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-azure opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-azure sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-azure sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-default opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-default sles 15.6 | 6.4.0-150600.23.135.1 | [SUSE-SU-2026:4369-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4369-1.md) | Oct 2, 2026 | | Linux | kernel-default sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-default sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23237-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23237-1.md) | Aug 11, 2026 | | Linux | kernel-default-base opensuse-leap 16.0 | 6.12.0-160000.37.1.160000.2.19 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-default-base sles 15.6 | 6.4.0-150600.23.135.1.150600.12.62.4 | [SUSE-SU-2026:4369-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4369-1.md) | Oct 2, 2026 | | Linux | kernel-default-base sles 15.7 | 6.4.0-150700.53.81.1.150700.17.45.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-default-base sles 16.0 | 6.12.0-160000.37.1.160000.2.19 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-docs opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-docs sles 15.6 | 6.4.0-150600.23.135.1 | [SUSE-SU-2026:4369-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4369-1.md) | Oct 2, 2026 | | Linux | kernel-docs sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-docs sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-kvmsmall opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-kvmsmall sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-livepatch-SLE15-SP6_Update_31 sles 15.6 | 1-150600.13.3.4 | [SUSE-SU-2026:4369-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4369-1.md) | Oct 2, 2026 | | Linux | kernel-livepatch-SLE15-SP7-RT_Update_20 sles 15.7 | 1-150700.1.3.1 | [SUSE-SU-2026:4120-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4120-1.md) | Sep 10, 2026 | | Linux | kernel-livepatch-SLE15-SP7_Update_21 sles 15.7 | 1-150700.15.3.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-obs-build opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-obs-build sles 15.6 | 6.4.0-150600.23.135.1 | [SUSE-SU-2026:4369-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4369-1.md) | Oct 2, 2026 | | Linux | kernel-obs-build sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-obs-qa opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-obs-qa sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-rt opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-source opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-source sles 15.6 | 6.4.0-150600.23.135.1 | [SUSE-SU-2026:4369-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4369-1.md) | Oct 2, 2026 | | Linux | kernel-source sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-source sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-syms opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-syms sles 15.6 | 6.4.0-150600.23.135.1 | [SUSE-SU-2026:4369-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4369-1.md) | Oct 2, 2026 | | Linux | kernel-syms sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-syms sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | kernel-zfcpdump opensuse-leap 16.0 | 6.12.0-160000.37.1 | [OPENSUSE-SU-2026:21555-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21555-1.md) | Aug 12, 2026 | | Linux | kernel-zfcpdump sles 15.7 | 6.4.0-150700.53.81.1 | [SUSE-SU-2026:4254-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4254-1.md) | Oct 7, 2026 | | Linux | kernel-zfcpdump sles 16.0 | 6.12.0-160000.37.1 | [SUSE-SU-2026:23231-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23231-1.md) | Aug 11, 2026 | | Linux | linux Debian 12.15 (bookworm) | 6.1.177-1 | [DEBIAN-CVE-2026-63827](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63827.md) | Jul 20, 2026 | | Linux | linux Debian 13.5 (trixie) | 6.12.95-1 | [DEBIAN-CVE-2026-63827](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63827.md) | Jul 20, 2026 | | Linux | linux Debian 14 | 7.1.3-1 | [DEBIAN-CVE-2026-63827](https://patchblox.com/security/data/fix/linux/debian-cve-2026-63827.md) | Jul 20, 2026 | --- Data as of 2026-11-10T01:44:33Z UTC. 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