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Snappier vulnerable to buffer overrun due to improper restriction of operations within the bounds of a memory buffer

High severity GitHub Reviewed Published Mar 27, 2023 in brantburnett/Snappier

Package

nuget Snappier (NuGet)

Affected versions

= 1.1.0

Patched versions

1.1.1

Description

Impact

This is a buffer overrun vulnerability that can affect any user of Snappier 1.1.0. In this release, much of the code was rewritten to use byte references rather than pointers to pinned buffers. This change generally improves performance and reduces workload on the garbage collector. However, when the garbage collector performs compaction and rearranges memory, it must update any byte references on the stack to refer to the updated location. The .NET garbage collector can only update these byte references if they still point within the buffer or to a point one byte past the end of the buffer. If they point outside this area, the buffer itself may be moved while the byte reference stays the same.

There are several places in 1.1.0 where byte references very briefly point outside the valid areas of buffers. These are at locations in the code being used for buffer range checks. While the invalid references are never dereferenced directly, if a GC compaction were to occur during the brief window when they are on the stack then it could invalidate the buffer range check and allow other operations to overrun the buffer.

This should be very difficult for an attacker to trigger intentionally. It would require a repetitive bulk attack with the hope that a GC compaction would occur at precisely the right moment during one of the requests. However, one of the range checks with this problem is a check based on input data in the decompression buffer, meaning malformed input data could be used to increase the chance of success.

Note that any resulting buffer overrun is likely to cause access to protected memory, which will then cause an exception and the process to be terminated. Therefore, the most likely result of an attack is a denial of service.

Patches

This is patched in release 1.1.1.

Workarounds

Pinning any buffers to a fixed location before using them for compression or decompression should mitigate some, but not all, of these cases. At least one temporary decompression buffer is internal to the library and never pinned.

References

@brantburnett brantburnett published to brantburnett/Snappier Mar 27, 2023
Published by the National Vulnerability Database Mar 27, 2023
Published to the GitHub Advisory Database Mar 27, 2023
Reviewed Mar 27, 2023

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:H

EPSS score

0.101%
(42nd percentile)

Weaknesses

CVE ID

CVE-2023-28638

GHSA ID

GHSA-838x-pcvx-6p5w

Source code

Credits

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