{"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":"2026-05-11T22:11:37.054Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-05-11T22:11:37.054Z"},"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"}}],"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-rc1","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-rc1"}]}]}],"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"}}}}