# CVE-2026-52923: ipc: limit next_id allocation to the valid ID range > A Linux kernel IPC bug allows attackers to trigger a use-after-free via checkpoint/restore, potentially leading to code execution or system crashes. - **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:** 24 Jun 2026 - **Updated:** 19 Oct 2026 - **Also known as:** ALSA-2026:49851, ALSA-2026:49857, AZL-90638, BELL-CVE-2026-52923, DEBIAN-CVE-2026-52923, GHSA-m237-4jxg-w5jh, RHSA-2026:49851, RHSA-2026:49857, RLSA-2026:49851, RLSA-2026:49857, ROOT-OS-DEBIAN-11-CVE-2026-52923, ROOT-OS-DEBIAN-12-CVE-2026-52923, ROOT-OS-UBUNTU-2204-CVE-2026-52923, ROOT-OS-UBUNTU-2404-CVE-2026-52923, RXSA-2026:49857, UBUNTU-CVE-2026-52923 ## What is CVE-2026-52923? CVE-2026-52923 is a high-severity use after free vulnerability in Linux kernel, published on 24 Jun 2026. 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: ipc: limit next_id allocation to the valid ID range The checkpoint/restore sysctl path can request the next SysV IPC id through ids->next_id. ipc_idr_alloc() currently forwards that request to idr_alloc() with an open-ended upper bound. If the valid tail of the SysV IPC id space is full, the allocation can spill beyond ipc_mni. The returned SysV IPC id still uses the normal index encoding, so later lookup and removal can target the wrong slot. This leaves the real IDR entry behind and breaks the IDR state for the object. The bug is in ipc_idr_alloc() in the checkpoint/restore path. 1. ids->next_id is passed to: idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id), 0, ...) 2. The zero upper bound makes the allocation effectively open-ended. Once the valid SysV IPC tail is occupied, idr_alloc() can spill past ipc_mni and allocate an entry beyond the valid IPC id range. 3. The new object id is still encoded with the narrower SysV IPC index width: new->id = (new->seq << ipcmni_seq_shift()) + idx 4. Later removal goes through ipc_rmid(), which uses: ipcid_to_idx(ipcp->id) That truncates the real IDR index. An object actually stored at a high index can then be removed as if it lived at a low in-range index. 5. For shared memory, shm_destroy() frees the current object anyway, but the real high IDR slot is left behind as a dangling pointer. 6. A subsequent walk of /proc/sysvipc/shm reaches the stale IDR entry and dereferences freed memory. Prevent this by bounding the requested allocation to ipc_mni so the checkpoint/restore path fails once the valid range is exhausted. Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime), CWE-825 (Expired Pointer Dereference), CWE-20 (Improper Input Validation) ## Which versions are affected by CVE-2026-52923? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `bpftool` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-abi-stablelists` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-core` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-cross-headers` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-debug` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-debug-core` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-debug-devel` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-debug-modules` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-debug-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-devel` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-doc` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-headers` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-modules` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-rt` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-core` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-debug` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-debug-core` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-debug-devel` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-debug-modules` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-debug-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-devel` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-modules` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-rt-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.rt7.492.el8_10 | | `kernel-tools` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-tools-libs` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-tools-libs-devel` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-zfcpdump` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-zfcpdump-core` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-zfcpdump-devel` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-zfcpdump-modules` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `kernel-zfcpdump-modules-extra` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `perf` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `python3-perf` | AlmaLinux:8 | All versions | 4.18.0-553.151.1.el8_10 | | `bpftool` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.151.1.el8_10 | | `bpftool-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.151.1.el8_10 | | `kernel` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.151.1.el8_10 | | `kernel-abi-stablelists` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.151.1.el8_10 | | `kernel-core` | Red Hat:enterprise_linux:8::baseos | All versions | 0:4.18.0-553.151.1.el8_10 | Products: Linux kernel. ## How do I fix CVE-2026-52923? Apply the vendor's patch. ## Is CVE-2026-52923 being exploited? There is no known exploitation of CVE-2026-52923 in the wild and no public exploit code. Public exploit code: - https://github.com/Hari-v542/CVE-2026-52923 (github_poc): https://github.com/Hari-v542/CVE-2026-52923 ## 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-2026-52923 and fix it if it is affected. What it is: CVE-2026-52923 is a high-severity use after free vulnerability in Linux kernel, published on 24 Jun 2026. 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-2026-52923 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-2026-52923/ (Markdown: https://insights.sbomify.com/CVE-2026-52923/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52923 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52923 - OSV: https://osv.dev/vulnerability/CVE-2026-52923 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-52923/ Summaries are generated and may contain mistakes; the official description above is the record.