要点
- CVE-2020-26243 は nanopb, nanopb (nanopb project) に影響する深刻度「高」 (CVSS 7.5) の脆弱性です。
- 今後30日間に悪用される確率（EPSS）：2.7%（全脆弱性の 85.8% より高い）。
- 対処：0.3.9.7, 0.4.4 以降に更新してください。
| パッケージ | 影響を受けるバージョン | 修正済みバージョン |
|---|
| nanopb PyPI | ≥ 0.3.2, < 0.3.9.7≥ 0.4.0, < 0.4.4
| 0.3.9.70.4.4
|
| nanopb | ≥ 0.4.0, < 0.4.4< 0.3.9.7
| 0.4.40.3.9.7
|
概要
Impact
Decoding specifically formed message can leak memory if dynamic allocation is enabled and an oneof field contains a static submessage that contains a dynamic field, and the message being decoded contains the submessage multiple times. This is rare in normal messages, but it is a concern when untrusted data is parsed.
Patches
Preliminary patch is available on git and problem will be patched in versions 0.3.9.7 and 0.4.4 once testing has been completed.
Workarounds
Following workarounds are available:
- Set the option
no_unions for the oneof field. This will generate fields as separate instead of C union, and avoids triggering the problematic code.
- Set the type of the submessage field inside oneof to
FT_POINTER. This way the whole submessage will be dynamically allocated and the problematic code is not executed.
- Use an arena allocator for nanopb, to make sure all memory can be released afterwards.
References
Bug report: https://github.com/nanopb/nanopb/issues/615
For more information
If you have any questions or comments about this advisory, comment on the bug report linked above.
NVD の説明
Nanopb is a small code-size Protocol Buffers implementation. In Nanopb before versions 0.4.4 and 0.3.9.7, decoding specifically formed message can leak memory if dynamic allocation is enabled and an oneof field contains a static submessage that contains a dynamic field, and the message being decoded contains the submessage multiple times. This is rare in normal messages, but it is a concern when untrusted data is parsed. This is fixed in versions 0.3.9.7 and 0.4.4. The following workarounds are available: 1) Set the option `no_unions` for the oneof field. This will generate fields as separate instead of C union, and avoids triggering the problematic code. 2) Set the type of the submessage field inside oneof to `FT_POINTER`. This way the whole submessage will be dynamically allocated and the problematic code is not executed. 3) Use an arena allocator for nanopb, to make sure all memory can be released afterwards.
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