Exploited vulnerability · CISA KEV

Is CVE-2021-1879 exploited? Yes: in CISA KEV since 3 Nov 2021

Gociux · Apple iOS, iPadOS, and watchOS · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-1879, Apple iOS, iPadOS, and watchOS WebKit Cross-Site Scripting (XSS) Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 3 Nov 2021, 215 days after it was published. It affects Apple iOS, iPadOS, and watchOS. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 3 Nov 2021

ransomwareNot knownno confirmed use

EPSStop 10%more likely than most to be exploited

severity6.1CVSS 3.1 · medium

US federal due17 Nov 2021BOD 22-01 deadline

What it is

Apple iOS, iPadOS, and watchOS WebKit contain an unspecified vulnerability that allows for universal cross-site scripting (XSS) when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.

Vendor	Apple (96 exploited CVEs in KEV)
Product	iOS, iPadOS, and watchOS
Vulnerability	Apple iOS, iPadOS, and watchOS WebKit Cross-Site Scripting (XSS) Vulnerability
Weakness	CWE-79
Published	2 Apr 2021
Added to KEV	3 Nov 2021
Reported by (CNA)	apple

What to do

Check whether you run it. Look for iOS, iPadOS, and watchOS in your asset inventory, including appliances and cloud images. Stack check lists every exploited Apple CVE at once.
Apply the fix. Apply updates per vendor instructions.
If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 2 Apr 2021.
Get told next time. Email alerts when CISA adds a CVE for Apple.

Other exploited CVEs in iOS, iPadOS, and watchOS

CVE-2023-41061: Apple iOS, iPadOS, and watchOS Wallet Code Execution Vulnerability (11 Sep 2023)
CVE-2020-9818: Apple iOS, iPadOS, and watchOS Out-of-Bounds Write Vulnerability (3 Nov 2021)
CVE-2020-9819: Apple iOS, iPadOS, and watchOS Memory Corruption Vulnerability (3 Nov 2021)

References

nvd.nist.gov/vuln/detail/CVE-2021-1879

Questions

Is CVE-2021-1879 being exploited?

Yes. CISA added CVE-2021-1879 to the Known Exploited Vulnerabilities catalog on 3 Nov 2021, which means there is reliable evidence of exploitation in the wild.

Is CVE-2021-1879 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2021-1879?

Apply updates per vendor instructions. Check Apple's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected iOS, iPadOS, and watchOS and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in November 2021 · Apple scorecard · act-now radar.

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