Answer in brief
CVE-2026-31586 records a High severity (CVSS 7.8) vulnerability in mm: blk-cgroup: fix use-after-free in cgwb_release_workfn(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 TM MFP - GNU/Linux subsystem (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC S7-1500 TM MFP - GNU/Linux subsystem (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <23acef4156c260e8598397a1a2e8b3a23e919893 || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <1bd36e93b542d9dd020190c6607c6a3663405195 || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <740ba1ebb223f137ff088ab74d533a13f9167bd8 || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <115a5266749dcde7fe4127e8623d19c752088f69 || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <dfc8292a1d6782c76b626315605e0585a5a18447 || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <ea3af09eb87d8f8708c66747fcf1a2762902e839 || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <50879a3c1faf06e661090015d59e2127255cff27 || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <67cb119d32f35e32acd0393bbeb318b2bb1fdafe || >=59b57717fff8b562825d9d25e0180ad7e8048ca9 <8f5857be99f1ed1fa80991c72449541f634626ee | 23acef4156c260e8598397a1a2e8b3a23e919893, 1bd36e93b542d9dd020190c6607c6a3663405195, 740ba1ebb223f137ff088ab74d533a13f9167bd8, 115a5266749dcde7fe4127e8623d19c752088f69, dfc8292a1d6782c76b626315605e0585a5a18447, ea3af09eb87d8f8708c66747fcf1a2762902e839, 50879a3c1faf06e661090015d59e2127255cff27, 67cb119d32f35e32acd0393bbeb318b2bb1fdafe, 8f5857be99f1ed1fa80991c72449541f634626ee |
| Linux/Linuxgeneric | 4.19 | Not reported |
| Siemens/SIMATIC S7-1500 TM MFP - GNU/Linux subsystemgeneric | >=0 <* | * |
Published upstream
Apr 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 15, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 15, 2026
In the Linux kernel, the following vulnerability has been resolved: mm: blk-cgroup: fix use-after-free in cgwb_release_workfn() cgwb_release_workfn() calls css_put(wb->blkcg_css) and then later accesses wb->blkcg_css again via blkcg_unpin_online(). If css_put() drops the last reference, the blkcg can be freed asynchronously (css_free_rwork_fn -> blkcg_css_free -> kfree) before blkcg_unpin_online() dereferences the pointer to access blkcg->online_pin, resulting in a use-after-free: BUG: KASAN: slab-use-after-free in blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367) Write of size 4 at addr ff11000117aa6160 by task kworker/71:1/531 Workqueue: cgwb_release cgwb_release_workfn Call Trace: <TASK> blkcg_unpin_online (./include/linux/instrumented.h:112 ./include/linux/atomic/atomic-instrumented.h:400 ./include/linux/refcount.h:389 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 block/blk-cgroup.c:1367) cgwb_release_workfn (mm/backing-dev.c:629) process_scheduled_works (kernel/workqueue.c:3278 kernel/workqueue.c:3385) Freed by task 1016: kfree (./include/linux/kasan.h:235 mm/slub.c:2689 mm/slub.c:6246 mm/slub.c:6561) css_free_rwork_fn (kernel/cgroup/cgroup.c:5542) process_scheduled_works (kernel/workqueue.c:3302 kernel/workqueue.c:3385) ** Stack based on commit 66672af7a095 ("Add linux-next specific files for 20260410") I am seeing this crash sporadically in Meta fleet across multiple kernel versions. A full reproducer is available at: https://github.com/leitao/debug/blob/main/reproducers/repro_blkcg_uaf.sh (The race window is narrow. To make it easily reproducible, inject a msleep(100) between css_put() and blkcg_unpin_online() in cgwb_release_workfn(). With that delay and a KASAN-enabled kernel, the reproducer triggers the splat reliably in less than a second.) Fix this by moving blkcg_unpin_online() before css_put(), so the cgwb's CSS reference keeps the blkcg alive while blkcg_unpin_online() accesses it.
Quoted source text, attributed separately from HOL analysis.