Memory leak in Nanopb
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_unionsfor 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.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | nanopb | >= 0.3.2, < 0.3.9.7, >= 0.4.0, < 0.4.4 | 0.3.9.7, 0.4.4 |
References
- https://github.com/nanopb/nanopb/security/advisories/GHSA-85rr-4rh9-hhwh
- https://nvd.nist.gov/vuln/detail/CVE-2020-26243
- https://github.com/nanopb/nanopb/issues/615
- https://github.com/nanopb/nanopb/commit/4fe23595732b6f1254cfc11a9b8d6da900b55b0c
- https://github.com/nanopb/nanopb/blob/2b48a361786dfb1f63d229840217a93aae064667/CHANGELOG.txt
- https://pypi.org/project/nanopb
- https://github.com/advisories/GHSA-85rr-4rh9-hhwh
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H- Weakness (CWE)
CWE-119, CWE-20- Platform
- Python (PyPI)
- Package
nanopb- Disclosed
- 25.11.2020
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-684 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-85rr-4rh9-hhwh - CC BY 4.0
Vulnerability history: nanopb
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 11.2020 03.2021
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 1
Disclosures per year
- 2020: 1
- 2021: 1
- 2022: 0
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 0
-
Memory leak in Nanopb this entry
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