Answer in brief
CVE-2021-47506 records a Critical severity (CVSS 9.8) vulnerability in nfsd: fix use-after-free due to delegation race. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (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 9.8. 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). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.15:rc2:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.15:rc3:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.15:rc4:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=dff1399f8addf7129c49bb2227469da79cc30b47 <04a8d07f3d58308b92630045560799a3faa3ebce || >=dff1399f8addf7129c49bb2227469da79cc30b47 <348714018139c39533c55661a0c7c990671396b4 || >=dff1399f8addf7129c49bb2227469da79cc30b47 <33645d3e22720cac1e4548f8fef57bf0649536ee || >=dff1399f8addf7129c49bb2227469da79cc30b47 <2becaa990b93cbd2928292c0b669d3abb6cf06d4 || >=dff1399f8addf7129c49bb2227469da79cc30b47 <e0759696de6851d7536efddfdd2dfed4c4df1f09 || >=dff1399f8addf7129c49bb2227469da79cc30b47 <eeb0711801f5e19ef654371b627682aed3b11373 || >=dff1399f8addf7129c49bb2227469da79cc30b47 <148c816f10fd11df27ca6a9b3238cdd42fa72cd3 || >=dff1399f8addf7129c49bb2227469da79cc30b47 <548ec0805c399c65ed66c6641be467f717833ab5 | 04a8d07f3d58308b92630045560799a3faa3ebce, 348714018139c39533c55661a0c7c990671396b4, 33645d3e22720cac1e4548f8fef57bf0649536ee, 2becaa990b93cbd2928292c0b669d3abb6cf06d4, e0759696de6851d7536efddfdd2dfed4c4df1f09, eeb0711801f5e19ef654371b627682aed3b11373, 148c816f10fd11df27ca6a9b3238cdd42fa72cd3, 548ec0805c399c65ed66c6641be467f717833ab5 |
| Linux/Linuxgeneric | 3.17 | Not reported |
Published upstream
May 24, 2024
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 4, 2026
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix use-after-free due to delegation race A delegation break could arrive as soon as we've called vfs_setlease. A delegation break runs a callback which immediately (in nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we then exit nfs4_set_delegation without hashing the delegation, it will be freed as soon as the callback is done with it, without ever being removed from del_recall_lru. Symptoms show up later as use-after-free or list corruption warnings, usually in the laundromat thread. I suspect aba2072f4523 "nfsd: grant read delegations to clients holding writes" made this bug easier to hit, but I looked as far back as v3.0 and it looks to me it already had the same problem. So I'm not sure where the bug was introduced; it may have been there from the beginning.
Quoted source text, attributed separately from HOL analysis.