CVE-2023-42917: Apple Multiple Products WebKit Memory Corruption Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Apple Multiple Products. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2023-12-04, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2023-12-25; treat that as the outer limit, not the target.
• EPSS 9.3%, percentile 95: FIRST’s model estimates a 9.3% chance of exploitation activity in the next 30 days, higher than 95% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.

What it is

A memory corruption vulnerability was addressed with improved locking. This issue is fixed in iOS 17.1.2 and iPadOS 17.1.2, macOS Sonoma 14.1.2, Safari 17.1.2. Processing web content may lead to arbitrary code execution. Apple is aware of a report that this issue may have been exploited against versions of iOS before iOS 16.7.1.

CISA’s summary

Apple iOS, iPadOS, macOS, and Safari WebKit contain a memory corruption vulnerability that leads to code execution 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.

Weakness type: CWE-787.

Product: Apple Multiple Products · Assigned by: apple · Published: 2023-11-30

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: required (a user must click/open something)
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2023-12-04; federal due date 2023-12-25. Known ransomware use: Unknown.
• CISA required action: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
• CISA SSVC assessment: exploitation active, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 9.29% probability of exploitation activity in the next 30 days; percentile 95.

Timeline

• 2023-11-30 — CVE record published by apple
• 2023-12-04 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2023-12-25 — CISA remediation deadline for US federal agencies
• 2025-10-21 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (support.apple.com) support.apple.com
2. Listed in CISA KEV notes (support.apple.com) support.apple.com
3. Listed in CISA KEV notes (support.apple.com) support.apple.com

Vulnerability records

1. CVE.org record CVE-2023-42917 cve.org
2. NVD entry CVE-2023-42917 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. support.apple.com support.apple.com
2. openwall.com openwall.com
3. lists.fedoraproject.org lists.fedoraproject.org
4. lists.fedoraproject.org lists.fedoraproject.org
5. support.apple.com support.apple.com
6. debian.org debian.org
7. seclists.org seclists.org
8. seclists.org seclists.org
9. seclists.org seclists.org
10. seclists.org seclists.org
11. seclists.org seclists.org
12. seclists.org seclists.org
13. security.gentoo.org security.gentoo.org
14. support.apple.com support.apple.com
15. seclists.org seclists.org

All exploited Apple vulnerabilities · Today’s Security Digest