{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-31584", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.120Z", "datePublished": "2026-04-24T14:42:13.586Z", "dateUpdated": "2026-08-05T12:23:36.030Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:23:36.030Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmedia: mediatek: vcodec: fix use-after-free in encoder release path\n\nThe fops_vcodec_release() function frees the context structure (ctx)\nwithout first cancelling any pending or running work in ctx->encode_work.\nThis creates a race window where the workqueue handler (mtk_venc_worker)\nmay still be accessing the context memory after it has been freed.\n\nRace condition:\n\n CPU 0 (release path) CPU 1 (workqueue)\n --------------------- ------------------\n fops_vcodec_release()\n v4l2_m2m_ctx_release()\n v4l2_m2m_cancel_job()\n // waits for m2m job \"done\"\n mtk_venc_worker()\n v4l2_m2m_job_finish()\n // m2m job \"done\"\n // BUT worker still running!\n // post-job_finish access:\n other ctx dereferences\n // UAF if ctx already freed\n // returns (job \"done\")\n kfree(ctx) // ctx freed\n\nRoot cause: The v4l2_m2m_ctx_release() only waits for the m2m job\nlifecycle (via TRANS_RUNNING flag), not the workqueue lifecycle.\nAfter v4l2_m2m_job_finish() is called, the m2m framework considers\nthe job complete and v4l2_m2m_ctx_release() returns, but the worker\nfunction continues executing and may still access ctx.\n\nThe work is queued during encode operations via:\n queue_work(ctx->dev->encode_workqueue, &ctx->encode_work)\nThe worker function accesses ctx->m2m_ctx, ctx->dev, and other ctx\nfields even after calling v4l2_m2m_job_finish().\n\nThis vulnerability was confirmed with KASAN by running an instrumented\ntest module that widens the post-job_finish race window. KASAN detected:\n\n BUG: KASAN: slab-use-after-free in mtk_venc_worker+0x159/0x180\n Read of size 4 at addr ffff88800326e000 by task kworker/u8:0/12\n\n Workqueue: mtk_vcodec_enc_wq mtk_venc_worker\n\n Allocated by task 47:\n __kasan_kmalloc+0x7f/0x90\n fops_vcodec_open+0x85/0x1a0\n\n Freed by task 47:\n __kasan_slab_free+0x43/0x70\n kfree+0xee/0x3a0\n fops_vcodec_release+0xb7/0x190\n\nFix this by calling cancel_work_sync(&ctx->encode_work) before kfree(ctx).\nThis ensures the workqueue handler is both cancelled (if pending) and\nsynchronized (waits for any running handler to complete) before the\ncontext is freed.\n\nPlacement rationale: The fix is placed after v4l2_ctrl_handler_free()\nand before list_del_init(&ctx->list). At this point, all m2m operations\nare done (v4l2_m2m_ctx_release() has returned), and we need to ensure\nthe workqueue is synchronized before removing ctx from the list and\nfreeing it.\n\nNote: The open error path does NOT need cancel_work_sync() because\nINIT_WORK() only initializes the work structure - it does not schedule\nit. Work is only scheduled later during device_run() operations." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The vulnerable path is reached through local V4L2 character device operations on the MediaTek mem2mem encoder, ending in `fops_vcodec_release()` after encode work is queued. It is not reachable directly by network packets or adjacent/physical input.\nAC:L - The attacker can queue encoder work with standard V4L2 ioctls and then close the same device while the workqueue handler is running. The race is attacker-driven and can be retried, so there are no external conditions that justify high complexity.\nPR:L - Triggering requires local access to the registered `/dev/video*` encoder node, but the driver and V4L2 core path contain no `capable()` or administrator-only checks. A basic local user with normal device-node access can reach the vulnerable ioctl/release path.\nUI:N - No victim action is required once the attacker can run code locally and access the video encoder device. The attacker controls the open, buffer queueing, streaming, and close operations.\nS:U - The vulnerability is in a kernel driver and impacts the same OS/kernel security authority. It does not cross a VM, hypervisor, IOMMU, or other separate security scope boundary.\nC:H - This is a slab use-after-free of the encoder context after `v4l2_m2m_job_finish()` lets release free the context while `mtk_venc_worker` can still dereference it. A kernel UAF is defensibly treated as enabling high confidentiality impact through heap reuse and memory disclosure primitives.\nI:H - The freed context contains pointers and state used by the worker, and UAF exploitation can be shaped with heap reuse to corrupt kernel control/data flow. Following the required overestimation rule for UAFs, integrity impact is high.\nA:H - KASAN confirmed a slab-use-after-free in `mtk_venc_worker`, and even non-exploited triggering can produce kernel oops/panic or destabilize the encoder workqueue path. Repeated local triggering can therefore cause high availability impact." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c" ], "versions": [ { "version": "0934d37596151edce115c6d0843a9ad7d5e5d232", "lessThan": "9a9bdaf9dc42ccca50e53f82165292f74a365c11", "status": "affected", "versionType": "git" }, { "version": "0934d37596151edce115c6d0843a9ad7d5e5d232", "lessThan": "a8a55913552aed45108525d1851c65e1db0cc25b", "status": "affected", "versionType": "git" }, { "version": "0934d37596151edce115c6d0843a9ad7d5e5d232", "lessThan": "f99353cd0e9f58bf17889049137b8d65fb44ebf1", "status": "affected", "versionType": "git" }, { "version": "0934d37596151edce115c6d0843a9ad7d5e5d232", "lessThan": "93d9a58961a9e09306857e999b3ee76aa4be67f0", "status": "affected", "versionType": "git" }, { "version": "0934d37596151edce115c6d0843a9ad7d5e5d232", "lessThan": "f1692337c6fa26e04f89b22a4d84bf5b7ada50d1", "status": "affected", "versionType": "git" }, { "version": "0934d37596151edce115c6d0843a9ad7d5e5d232", "lessThan": "76e35091ffc722ba39b303e48bc5d08abb59dd56", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c" ], "versions": [ { "version": "6.6", "status": "affected" }, { "version": "0", "lessThan": "6.6", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.136", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.83", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.24", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.19.14", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.1", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.6.136" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.12.83" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.18.24" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "6.19.14" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.0.1" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/9a9bdaf9dc42ccca50e53f82165292f74a365c11" }, { "url": "https://git.kernel.org/stable/c/a8a55913552aed45108525d1851c65e1db0cc25b" }, { "url": "https://git.kernel.org/stable/c/f99353cd0e9f58bf17889049137b8d65fb44ebf1" }, { "url": "https://git.kernel.org/stable/c/93d9a58961a9e09306857e999b3ee76aa4be67f0" }, { "url": "https://git.kernel.org/stable/c/f1692337c6fa26e04f89b22a4d84bf5b7ada50d1" }, { "url": "https://git.kernel.org/stable/c/76e35091ffc722ba39b303e48bc5d08abb59dd56" } ], "title": "media: mediatek: vcodec: fix use-after-free in encoder release path", "x_generator": { "engine": "bippy-1.2.0" } } } }