# CVE-2021-1884: Race condition in iOS and iPadOS

> A remote attacker can cause a denial of service via a race condition in Apple operating systems, requiring users to apply security updates.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 Sep 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-2v79-m39q-gmxx

## What is CVE-2021-1884?

CVE-2021-1884 is a medium-severity vulnerability in Apple Ipados, published on 8 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A race condition was addressed with improved locking. This issue is fixed in Security Update 2021-004 Mojave, iOS 14.5 and iPadOS 14.5, watchOS 7.4, Security Update 2021-003 Catalina, tvOS 14.5, macOS Big Sur 11.3. A remote attacker may be able to cause a denial of service.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2021-1884?

It affects 6 products.


Products: Apple Ipados, Apple Iphone Os, Apple Mac Os X, Apple Macos, Apple Tvos, Apple Watchos.

## How do I fix CVE-2021-1884?

No fix has been published for CVE-2021-1884 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1884 being exploited?

There is no known exploitation of CVE-2021-1884 in the wild and no public exploit code.

## Other vulnerabilities in Apple Ipados

- [CVE-2025-43300](https://insights.sbomify.com/CVE-2025-43300/): Apple iOS, iPadOS, and macOS Out-of-Bounds Write (critical 10.0, exploited in the wild)
- [CVE-2025-24201](https://insights.sbomify.com/CVE-2025-24201/): Apple Multiple Products WebKit Out-of-Bounds Write (critical 10.0, exploited in the wild)
- [CVE-2025-24085](https://insights.sbomify.com/CVE-2025-24085/): Apple Multiple Products Use-After-Free (critical 10.0, exploited in the wild)
- [CVE-2025-31200](https://insights.sbomify.com/CVE-2025-31200/): Apple Multiple Products Memory Corruption (critical 9.8, exploited in the wild)
- [CVE-2025-31201](https://insights.sbomify.com/CVE-2025-31201/): Apple Multiple Products Arbitrary Read and Write (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-1884 and fix it if it is affected.

What it is: CVE-2021-1884 is a medium-severity vulnerability in Apple Ipados, published on 8 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-1884 in the wild and no public exploit code.

Affected product: Apple Ipados. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-1884/ (Markdown: https://insights.sbomify.com/CVE-2021-1884/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1884
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1884
- OSV: https://osv.dev/vulnerability/CVE-2021-1884

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-1884/
Summaries are generated and may contain mistakes; the official description above is the record.