cbcvebase.
CVE-2021-30860
published 2021-08-24

CVE-2021-30860: An integer overflow was addressed with improved input validation. This issue is fixed in Security Update 2021-005 Catalina, iOS 14.8 and iPadOS 14.8, macOS Big…

PriorityP188high7.8CVSS 3.1
AVLACLPRNUIRSUCHIHAH
KEVITW
CISA Known Exploited Vulnerabilitydue 2021-11-17
Exploited in the wild
EPSS
75.99%
99.5th percentile
An integer overflow was addressed with improved input validation. This issue is fixed in Security Update 2021-005 Catalina, iOS 14.8 and iPadOS 14.8, macOS Big Sur 11.6, watchOS 7.6.2. Processing a maliciously crafted PDF may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited.

Affected

15 ranges
VendorProductVersion rangeFixed in
appleios
appleios_14.8_and_ipados
appleipados< 14.814.8
appleiphone_os< 12.5.512.5.5
appleiphone_os>= 13.0 < 14.814.8
applemac_os_x
applemac_os_x>= 10.15 < 10.15.710.15.7
applemacos< 11.611.6
applemacos_big_sur
applesecurity_update_2021-005_catalina
applewatchos< 7.6.27.6.2
applewatchos
freedesktoppoppler< 22.09.022.09.0
xpdfreaderxpdf< 4.044.04
xpdfreaderxpdf

Detection & IOCsextracted from sources · hover to see the quote

othernumSyms=1=(0x80000000+0x80000001)
  • The vulnerability is triggered inside JBIG2Stream::readTextRegionSeg in CoreGraphics.framework; monitor for crashes or anomalous execution originating from this function.
  • Exploit delivery is via iMessage attachment parsing (zero-click); look for iMessage processes spawning unexpected child processes or crashing while parsing attachments.
  • A dyld_shared_cache slide of 0 in crash logs indicates all system modules loaded at fixed addresses, which is a sign of exploit-induced ASLR bypass; flag crash logs exhibiting this condition.
  • Exploitation replaces the virtual function table of JBIG2Segment objects and bypasses PAC; forensic analysis of crash logs should check for vtable corruption on JBIG2Segment objects.
  • The exploit is triggered by processing a maliciously crafted PDF (or JBIG2-encoded iMessage attachment); inspect incoming iMessage attachments and PDF files for embedded JBIG2 streams with oversized symbol dictionary segment sizes that cause integer overflow in numSyms.
  • ·The crash address 0x181d6e228 is not the initial exploitation point; it is a downstream crash after vtable hijacking has already occurred, so using it alone as a detection anchor may miss earlier exploitation stages.
  • ·The ForcedEntry exploit was observed bypassing BlastDoor, Apple's iMessage sandboxing defense; BlastDoor alone should not be relied upon as a mitigating control for this CVE on unpatched devices.

CVSS provenance

nvdv3.17.8HIGHCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
nvdv2.06.8MEDIUMAV:N/AC:M/Au:N/C:P/I:P/A:P
osv7.8HIGH
vulncheck7.8HIGH
cisa7.8HIGH
vendor_redhat7.8HIGH
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