# CVE-2023-53621: memcontrol: ensure memcg acquired by id is properly set up > A race condition in the Linux kernel memory control subsystem can cause a NULL pointer dereference, leading to a system crash. - **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 7 Oct 2025 - **Updated:** 11 May 2026 - **Also known as:** BELL-CVE-2023-53621, DEBIAN-CVE-2023-53621, GHSA-qhmw-vr57-jm8g, UBUNTU-CVE-2023-53621 ## What is CVE-2023-53621? CVE-2023-53621 is a high-severity vulnerability in Linux kernel, published on 7 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description In the Linux kernel, the following vulnerability has been resolved: memcontrol: ensure memcg acquired by id is properly set up In the eviction recency check, we attempt to retrieve the memcg to which the folio belonged when it was evicted, by the memcg id stored in the shadow entry. However, there is a chance that the retrieved memcg is not the original memcg that has been killed, but a new one which happens to have the same id. This is a somewhat unfortunate, but acceptable and rare inaccuracy in the heuristics. However, if we retrieve this new memcg between its allocation and when it is properly attached to the memcg hierarchy, we could run into the following NULL pointer exception during the memcg hierarchy traversal done in mem_cgroup_get_nr_swap_pages(): [ 155757.793456] BUG: kernel NULL pointer dereference, address: 00000000000000c0 [ 155757.807568] #PF: supervisor read access in kernel mode [ 155757.818024] #PF: error_code(0x0000) - not-present page [ 155757.828482] PGD 401f77067 P4D 401f77067 PUD 401f76067 PMD 0 [ 155757.839985] Oops: 0000 [#1] SMP [ 155757.887870] RIP: 0010:mem_cgroup_get_nr_swap_pages+0x3d/0xb0 [ 155757.899377] Code: 29 19 4a 02 48 39 f9 74 63 48 8b 97 c0 00 00 00 48 8b b7 58 02 00 00 48 2b b7 c0 01 00 00 48 39 f0 48 0f 4d c6 48 39 d1 74 42 <48> 8b b2 c0 00 00 00 48 8b ba 58 02 00 00 48 2b ba c0 01 00 00 48 [ 155757.937125] RSP: 0018:ffffc9002ecdfbc8 EFLAGS: 00010286 [ 155757.947755] RAX: 00000000003a3b1c RBX: 000007ffffffffff RCX: ffff888280183000 [ 155757.962202] RDX: 0000000000000000 RSI: 0007ffffffffffff RDI: ffff888bbc2d1000 [ 155757.976648] RBP: 0000000000000001 R08: 000000000000000b R09: ffff888ad9cedba0 [ 155757.991094] R10: ffffea0039c07900 R11: 0000000000000010 R12: ffff888b23a7b000 [ 155758.005540] R13: 0000000000000000 R14: ffff888bbc2d1000 R15: 000007ffffc71354 [ 155758.019991] FS: 00007f6234c68640(0000) GS:ffff88903f9c0000(0000) knlGS:0000000000000000 [ 155758.036356] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 155758.048023] CR2: 00000000000000c0 CR3: 0000000a83eb8004 CR4: 00000000007706e0 [ 155758.062473] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 155758.076924] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 155758.091376] PKRU: 55555554 [ 155758.096957] Call Trace: [ 155758.102016] [ 155758.106502] ? __die+0x78/0xc0 [ 155758.112793] ? page_fault_oops+0x286/0x380 [ 155758.121175] ? exc_page_fault+0x5d/0x110 [ 155758.129209] ? asm_exc_page_fault+0x22/0x30 [ 155758.137763] ? mem_cgroup_get_nr_swap_pages+0x3d/0xb0 [ 155758.148060] workingset_test_recent+0xda/0x1b0 [ 155758.157133] workingset_refault+0xca/0x1e0 [ 155758.165508] filemap_add_folio+0x4d/0x70 [ 155758.173538] page_cache_ra_unbounded+0xed/0x190 [ 155758.182919] page_cache_sync_ra+0xd6/0x1e0 [ 155758.191738] filemap_read+0x68d/0xdf0 [ 155758.199495] ? mlx5e_napi_poll+0x123/0x940 [ 155758.207981] ? __napi_schedule+0x55/0x90 [ 155758.216095] __x64_sys_pread64+0x1d6/0x2c0 [ 155758.224601] do_syscall_64+0x3d/0x80 [ 155758.232058] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 155758.242473] RIP: 0033:0x7f62c29153b5 [ 155758.249938] Code: e8 48 89 75 f0 89 7d f8 48 89 4d e0 e8 b4 e6 f7 ff 41 89 c0 4c 8b 55 e0 48 8b 55 e8 48 8b 75 f0 8b 7d f8 b8 11 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 33 44 89 c7 48 89 45 f8 e8 e7 e6 f7 ff 48 8b [ 155758.288005] RSP: 002b:00007f6234c5ffd0 EFLAGS: 00000293 ORIG_RAX: 0000000000000011 [ 155758.303474] RAX: ffffffffffffffda RBX: 00007f628c4e70c0 RCX: 00007f62c29153b5 [ 155758.318075] RDX: 000000000003c041 RSI: 00007f61d2986000 RDI: 0000000000000076 [ 155758.332678] RBP: 00007f6234c5fff0 R08: 0000000000000000 R09: 0000000064d5230c [ 155758.347452] R10: 000000000027d450 R11: 0000000000000293 R12: 000000000003c041 [ 155758.362044] R13: 00007f61d2986000 R14: 00007f629e11b060 R15: 000000000027d450 [ 155758.376661] This patch fixes the issue by moving the memcg's id publication from the alloc stage to ---truncated--- Weakness: CWE-476 (NULL Pointer Dereference) ## Which versions are affected by CVE-2023-53621? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2023-53621? Apply the vendor's patch. ## Is CVE-2023-53621 being exploited? There is no known exploitation of CVE-2023-53621 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2023-53621 and fix it if it is affected. What it is: CVE-2023-53621 is a high-severity vulnerability in Linux kernel, published on 7 Oct 2025. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2023-53621 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2023-53621/ (Markdown: https://insights.sbomify.com/CVE-2023-53621/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53621 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53621 - OSV: https://osv.dev/vulnerability/CVE-2023-53621 --- From sbomify Insights: https://insights.sbomify.com/CVE-2023-53621/ Summaries are generated and may contain mistakes; the official description above is the record.