# CVE-2024-26957: s390/zcrypt: fix reference counting on zcrypt card objects > A use-after-free vulnerability in the Linux kernel's s390/zcrypt driver allows attackers to cause denial of service or potentially execute code via hot-plugging crypto cards. - **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:** 1 May 2024 - **Updated:** 15 Oct 2026 - **Also known as:** BELL-CVE-2024-26957, DEBIAN-CVE-2024-26957, GHSA-7x33-7jjx-2gmh, UBUNTU-CVE-2024-26957 ## What is CVE-2024-26957? CVE-2024-26957 is a high-severity use after free vulnerability in Debian Debian Linux, published on 1 May 2024. 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: s390/zcrypt: fix reference counting on zcrypt card objects Tests with hot-plugging crytpo cards on KVM guests with debug kernel build revealed an use after free for the load field of the struct zcrypt_card. The reason was an incorrect reference handling of the zcrypt card object which could lead to a free of the zcrypt card object while it was still in use. This is an example of the slab message: kernel: 0x00000000885a7512-0x00000000885a7513 @offset=1298. First byte 0x68 instead of 0x6b kernel: Allocated in zcrypt_card_alloc+0x36/0x70 [zcrypt] age=18046 cpu=3 pid=43 kernel: kmalloc_trace+0x3f2/0x470 kernel: zcrypt_card_alloc+0x36/0x70 [zcrypt] kernel: zcrypt_cex4_card_probe+0x26/0x380 [zcrypt_cex4] kernel: ap_device_probe+0x15c/0x290 kernel: really_probe+0xd2/0x468 kernel: driver_probe_device+0x40/0xf0 kernel: __device_attach_driver+0xc0/0x140 kernel: bus_for_each_drv+0x8c/0xd0 kernel: __device_attach+0x114/0x198 kernel: bus_probe_device+0xb4/0xc8 kernel: device_add+0x4d2/0x6e0 kernel: ap_scan_adapter+0x3d0/0x7c0 kernel: ap_scan_bus+0x5a/0x3b0 kernel: ap_scan_bus_wq_callback+0x40/0x60 kernel: process_one_work+0x26e/0x620 kernel: worker_thread+0x21c/0x440 kernel: Freed in zcrypt_card_put+0x54/0x80 [zcrypt] age=9024 cpu=3 pid=43 kernel: kfree+0x37e/0x418 kernel: zcrypt_card_put+0x54/0x80 [zcrypt] kernel: ap_device_remove+0x4c/0xe0 kernel: device_release_driver_internal+0x1c4/0x270 kernel: bus_remove_device+0x100/0x188 kernel: device_del+0x164/0x3c0 kernel: device_unregister+0x30/0x90 kernel: ap_scan_adapter+0xc8/0x7c0 kernel: ap_scan_bus+0x5a/0x3b0 kernel: ap_scan_bus_wq_callback+0x40/0x60 kernel: process_one_work+0x26e/0x620 kernel: worker_thread+0x21c/0x440 kernel: kthread+0x150/0x168 kernel: __ret_from_fork+0x3c/0x58 kernel: ret_from_fork+0xa/0x30 kernel: Slab 0x00000372022169c0 objects=20 used=18 fp=0x00000000885a7c88 flags=0x3ffff00000000a00(workingset|slab|node=0|zone=1|lastcpupid=0x1ffff) kernel: Object 0x00000000885a74b8 @offset=1208 fp=0x00000000885a7c88 kernel: Redzone 00000000885a74b0: bb bb bb bb bb bb bb bb ........ kernel: Object 00000000885a74b8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74c8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74d8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74e8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74f8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a7508: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 68 4b 6b 6b 6b a5 kkkkkkkkkkhKkkk. kernel: Redzone 00000000885a7518: bb bb bb bb bb bb bb bb ........ kernel: Padding 00000000885a756c: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZ kernel: CPU: 0 PID: 387 Comm: systemd-udevd Not tainted 6.8.0-HF #2 kernel: Hardware name: IBM 3931 A01 704 (KVM/Linux) kernel: Call Trace: kernel: [<00000000ca5ab5b8>] dump_stack_lvl+0x90/0x120 kernel: [<00000000c99d78bc>] check_bytes_and_report+0x114/0x140 kernel: [<00000000c99d53cc>] check_object+0x334/0x3f8 kernel: [<00000000c99d820c>] alloc_debug_processing+0xc4/0x1f8 kernel: [<00000000c99d852e>] get_partial_node.part.0+0x1ee/0x3e0 kernel: [<00000000c99d94ec>] ___slab_alloc+0xaf4/0x13c8 kernel: [<00000000c99d9e38>] __slab_alloc.constprop.0+0x78/0xb8 kernel: [<00000000c99dc8dc>] __kmalloc+0x434/0x590 kernel: [<00000000c9b4c0ce>] ext4_htree_store_dirent+0x4e/0x1c0 kernel: [<00000000c9b908a2>] htree_dirblock_to_tree+0x17a/0x3f0 kernel: ---truncated--- Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2024-26957? It affects 2 products. Products: Debian Debian Linux, Linux kernel. ## How do I fix CVE-2024-26957? Apply the vendor's patch. ## Is CVE-2024-26957 being exploited? There is no known exploitation of CVE-2024-26957 in the wild and no public exploit code. ## Other vulnerabilities in Debian Debian Linux - [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild) - [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild) - [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild) - [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild) - [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2024-26957 and fix it if it is affected. What it is: CVE-2024-26957 is a high-severity use after free vulnerability in Debian Debian Linux, published on 1 May 2024. 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-2024-26957 in the wild and no public exploit code. Affected product: Debian Debian Linux. 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-2024-26957/ (Markdown: https://insights.sbomify.com/CVE-2024-26957/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2024-26957 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-26957 - OSV: https://osv.dev/vulnerability/CVE-2024-26957 --- From sbomify Insights: https://insights.sbomify.com/CVE-2024-26957/ Summaries are generated and may contain mistakes; the official description above is the record.