Critical severity · published Dec 21, 2017
CVE-2017-17821
WTF/wtf/FastBitVector.h in WebKit, as distributed in Safari Technology Preview Release 46, allows remote attackers to cause a denial of service (buffer overflow) or possibly have…
9.8
CVSS
1.4%
EPSS
No
On KEV
Description
WTF/wtf/FastBitVector.h in WebKit, as distributed in Safari Technology Preview Release 46, allows remote attackers to cause a denial of service (buffer overflow) or possibly have unspecified other impact because it calls the FastBitVectorWordOwner::resizeSlow function (in WTF/wtf/FastBitVector.cpp) for a purpose other than initializing a bitvector size, and resizeSlow mishandles cases where the old array length is greater than the new array length.
CVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.4% · higher than 72% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SA
Safari · Apple
46 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2017-17821
CVE.org
https://www.cve.org/CVERecord?id=CVE-2017-17821
Permissions Required
https://bugs.webkit.org/show_bug.cgi?id=181020
Third Party Advisory
https://github.com/dwfault/PoCs/blob/master/WebKit%20Misuse%20of%20WTF:wtf:FastBitVector%20result%20in%20potential%20BOF/WebKit%20Misuse%20of%20WTF:wtf:FastBitVector%20result%20in%20potential%20BOF.md
More from Safari
10.0
CVE-2025-24201
Apple Multiple Products WebKit Out-of-Bounds Write Vulnerability
8.8
CVE-2025-43529
Apple Multiple Products Use-After-Free WebKit Vulnerability
8.8
CVE-2025-14174
Google Chromium Out of Bounds Memory Access Vulnerability
8.8
CVE-2023-43000
Apple Multiple products Use-After-Free Vulnerability
8.8
CVE-2025-31277
Apple Multiple Products Buffer Overflow Vulnerability