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CVE-2021-1879

6.1, medium Known exploited

Apple iOS, iPadOS, and watchOS WebKit Cross-Site Scripting (XSS) Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
6.1, medium medium CVSS v3.1
EPSS, next 30 days
7% higher than 94.1% of scored CVEs
Exploitation
Confirmed in the wild
Published
2 Apr 20215 years ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 3 Nov 2021. US federal agencies had to remediate by 17 Nov 2021, a deadline that has passed.

Required action. Apply updates per vendor instructions.

Description

This issue was addressed by improved management of object lifetimes. This issue is fixed in iOS 12.5.2, iOS 14.4.2 and iPadOS 14.4.2, watchOS 7.3.3. Processing maliciously crafted web content may lead to universal cross site scripting. Apple is aware of a report that this issue may have been actively exploited..

Details

Vendor
Apple
Product
iOS and iPadOS
Weakness
CWE-79 (opens in a new tab)
Status
Analyzed
Updated
17 Jun 2026
Assigner
product-security@apple.com

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References 4

Advisories 3

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Apple CVEs

Every Apple CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-86950 Apple Multiple Products Out-of-Bounds Write Vulnerability KEV EPSS 1% 8.8, high
  • CVE-2026-65400 Apple macOS Improper Authentication Vulnerability KEV EPSS 2% 9.8, critical
  • CVE-2026-20700 Apple Multiple Buffer Overflow Vulnerability KEV EPSS 1% 7.8, high
  • CVE-2025-43529 Apple Multiple Products Use-After-Free WebKit Vulnerability KEV EPSS 9% 8.8, high
  • CVE-2025-43510 Apple Multiple Products Improper Locking Vulnerability KEV EPSS 0.4% 7.8, high
  • CVE-2025-43520 Apple Multiple Products Classic Buffer Overflow Vulnerability KEV EPSS 0.4% 5.5, medium
  • CVE-2023-43000 Apple Multiple products Use-After-Free Vulnerability KEV EPSS 4% 8.8, high
  • CVE-2025-43300 Apple iOS, iPadOS, and macOS Out-of-Bounds Write Vulnerability KEV EPSS 32% 10, critical

Beyond this page

Is CVE-2021-1879 in your network?

This page tells you how dangerous CVE-2021-1879 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2021-1879 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2021-1879 comes with the devices to patch.

    Learn more about EXYS7600 OCELOT

  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.