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CVE-2026-63827— apparmor: fix use-after-free in rawdata dedup loop

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 7.0版本存在安全漏洞，该漏洞源于apparmor组件的rawdata去重循环中存在释放后重用问题，可能导致攻击者利用pcount引用计数为0时进行释放后重用。

CVSS 7.8 · High EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 26

VendorProduct Version RangeStatus
Linux Linux 3b8e77c7abab40e6de9ad9de730d77984a498840< 643221da57dbb1a8fd800610331cf1ec27969f71 affected
d9d8560b9b7932f8cffc4c068c14289220900f79< b17f0c59cc1525765625cf07d0391b7f9c1ed7e5 affected
6b6ba87579c7e7c669e0bec91823e7fb693bc5df< a7a2890028f16e5b0af0bb005d80fcb32559cca3 affected
6ef1f2926c41ab96952d9696d55a052f1b3a9418< 15fd83a1e42ede15070968806bb6c8b1a5170688 affected
f9761add6d100962a23996cb68f3d6abdd4d1815< ce261a20b41db522e320a41bbf1292bf85af66df affected
af782cc8871e3683ddd5a3cd2f7df526599863a9< c3ca2631073b2cef06824fd2bfc452ff7a1023de affected
a0b7091c4de45a7325c8780e6934a894f92ac86b< 5e34fa9f6f7cd688ae153fff13139a5cf2d42339 affected
a0b7091c4de45a7325c8780e6934a894f92ac86b< 6f060496d03e4dc560a40f73770bd08335cb7a27 affected
… +18 more rows
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I. Basic Information for CVE-2026-63827

Vulnerability Information
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Vulnerability Title
apparmor: fix use-after-free in rawdata dedup loop
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一款操作系统内核。 Linux kernel 7.0版本存在安全漏洞，该漏洞源于apparmor组件的rawdata去重循环中存在释放后重用问题，可能导致攻击者利用pcount引用计数为0时进行释放后重用。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 3b8e77c7abab40e6de9ad9de730d77984a498840 ~ 643221da57dbb1a8fd800610331cf1ec27969f71 -
Linux Linux 7.0 -

II. Public POCs for CVE-2026-63827

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III. Intelligence Information for CVE-2026-63827

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Patches & Fixes for CVE-2026-63827 (7)

Same Patch Batch · Linux · 2026-07-19 · 429 CVEs total

CVE-2026-63795 10.0 CRITICAL 9p: avoid putting oldfid in p9_client_walk() error path
CVE-2026-64091 9.8 CRITICAL batman-adv: tt: fix TOCTOU race for reported vlans
CVE-2026-63984 9.8 CRITICAL ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()
CVE-2026-64025 9.8 CRITICAL bpf, skmsg: fix verdict sk_data_ready racing with ktls rx
CVE-2026-63922 9.8 CRITICAL ipv6: exthdrs: refresh nh after handling HAO option
CVE-2026-63979 9.8 CRITICAL net/handshake: hand off the pinned file reference to accept_doit
CVE-2026-64056 9.8 CRITICAL net: ethernet: cortina: Make RX SKB per-port
CVE-2026-63800 9.8 CRITICAL pNFS: Fix use-after-free in pnfs_update_layout()
CVE-2026-63978 9.8 CRITICAL net/handshake: Drain pending requests at net namespace exit
CVE-2026-64055 9.8 CRITICAL net: ethernet: cortina: Carry over frag counter
CVE-2026-63808 9.8 CRITICAL exfat: fix potential use-after-free in exfat_find_dir_entry()
CVE-2026-64033 9.8 CRITICAL RDMA/rtrs: Fix use-after-free in path file creation cleanup
CVE-2026-63888 9.8 CRITICAL scsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
CVE-2026-63887 9.8 CRITICAL scsi: target: iscsi: Bound iscsi_encode_text_output() appends to rsp_buf
CVE-2026-64113 9.8 CRITICAL ixgbevf: fix use-after-free in VEPA multicast source pruning
CVE-2026-63825 9.8 CRITICAL gcov: use atomic counter updates to fix concurrent access crashes
CVE-2026-63857 9.8 CRITICAL net: airoha: Do not read uninitialized fragment address in airoha_dev_xmit()
CVE-2026-64160 9.8 CRITICAL netfs: Fix potential for tearing in ->remote_i_size and ->zero_point
CVE-2026-64125 9.8 CRITICAL net: bcmgenet: keep RBUF EEE/PM disabled
CVE-2026-63924 9.8 CRITICAL ipv6: exthdrs: refresh nh pointer after ipv6_hop_jumbo()

Showing top 20 of 429 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

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