Multiple vulnerabilities resulting in out-of-bounds writes

2022-09-0712:00:00

Google

osv.dev

vulnerabilities

heap initialization

out-of-bounds writes

metadata operations

heap::extend

address 0

unaligned writes

dos

software

CVSS3

9.8

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

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

EPSS

0.002

Percentile

54.5%

The heap initialization methods were missing a minimum size check for the given heap size argument. This could lead to out-of-bound writes when a heap was initialized with a size smaller than 3 * size_of::<usize> because of metadata write operations.
When calling Heap::extend with a size smaller than two usizes (e.g., 16 on x86_64), the size was erroneously rounded up to the minimum size, which could result in an out-of-bounds write.
Calling Heap::extend on an empty heap tried to construct a heap starting at address 0, which is also an out-of-bounds write.
- One specific way to trigger this accidentally is to call Heap::new (or a similar constructor) with a heap size that is smaller than two usizes. This was treated as an empty heap as well.
Calling Heap::extend on a heap whose size is not a multiple of the size of two usizes resulted in unaligned writes. It also left the heap in an unexpected state, which might lead to subsequent issues. We did not find a way to exploit this undefined behavior yet (apart from DoS on platforms that fault on unaligned writes).