Answer in brief
CVE-2021-47505 records a High severity (CVSS 7.8) vulnerability in aio: fix use-after-free due to missing POLLFREE handling. 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 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). 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:5.16:rc1:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:* | Not reported | Not reported |
| cpe:2.3:o:linux:linux_kernel:5.16:rc4:*:*:*:*:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=2c14fa838cbefc23cf1c73ca167ed85b274b2913 <321fba81ec034f88aea4898993c1bf15605c023f || >=2c14fa838cbefc23cf1c73ca167ed85b274b2913 <4105e6a128e8a98455dfc9e6dbb2ab0c33c4497f || >=2c14fa838cbefc23cf1c73ca167ed85b274b2913 <47ffefd88abfffe8a040bcc1dd0554d4ea6f7689 || >=2c14fa838cbefc23cf1c73ca167ed85b274b2913 <60d311f9e6381d779d7d53371f87285698ecee24 || >=2c14fa838cbefc23cf1c73ca167ed85b274b2913 <50252e4b5e989ce64555c7aef7516bdefc2fea72 | 321fba81ec034f88aea4898993c1bf15605c023f, 4105e6a128e8a98455dfc9e6dbb2ab0c33c4497f, 47ffefd88abfffe8a040bcc1dd0554d4ea6f7689, 60d311f9e6381d779d7d53371f87285698ecee24, 50252e4b5e989ce64555c7aef7516bdefc2fea72 |
| Linux/Linuxgeneric | 4.18 | 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: aio: fix use-after-free due to missing POLLFREE handling signalfd_poll() and binder_poll() are special in that they use a waitqueue whose lifetime is the current task, rather than the struct file as is normally the case. This is okay for blocking polls, since a blocking poll occurs within one task; however, non-blocking polls require another solution. This solution is for the queue to be cleared before it is freed, by sending a POLLFREE notification to all waiters. Unfortunately, only eventpoll handles POLLFREE. A second type of non-blocking poll, aio poll, was added in kernel v4.18, and it doesn't handle POLLFREE. This allows a use-after-free to occur if a signalfd or binder fd is polled with aio poll, and the waitqueue gets freed. Fix this by making aio poll handle POLLFREE. A patch by Ramji Jiyani <[email protected]> (https://lore.kernel.org/r/[email protected]) tried to do this by making aio_poll_wake() always complete the request inline if POLLFREE is seen. However, that solution had two bugs. First, it introduced a deadlock, as it unconditionally locked the aio context while holding the waitqueue lock, which inverts the normal locking order. Second, it didn't consider that POLLFREE notifications are missed while the request has been temporarily de-queued. The second problem was solved by my previous patch. This patch then properly fixes the use-after-free by handling POLLFREE in a deadlock-free way. It does this by taking advantage of the fact that freeing of the waitqueue is RCU-delayed, similar to what eventpoll does.
Quoted source text, attributed separately from HOL analysis.