CVE-2020-26243
mediumpriority · track · 31EPSS 0.027 · 86 %ileEUUSEPSS · scored 2026-10-27
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.
cvss
Technical severity, 0–10. One row per scoring source.
base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 4.3–7.5
weaknesses
The CWE weakness classes this flaw belongs to.
affected products (6)
Products and version ranges known to be affected.
advisories (2)
Vendor and ecosystem advisories describing this.
- GHSA-85rr-4rh9-hhwhMemory leak in Nanopb2020-11-25ghsa · osvUS
### 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](https://github.com/nanopb/nanopb/commit/edf6dcbffee4d614ac0c2c1b258ab95185bdb6e9) 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.
- PYSEC-2026-684Memory leak in Nanopb2026-07-02vendor · osvUS
### 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](https://github.com/nanopb/nanopb/commit/edf6dcbffee4d614ac0c2c1b258ab95185bdb6e9) 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.
also known as (6)
Other names and identifiers for this entity.
sources
Which sources assert this record, and when.
references (16)
External citations — patches, advisories, analysis.
- https://access.redhat.com/security/cve/cve-2020-26243cnnvd
- https://github.com/nanopb/nanopb/blob/2b48a361786dfb1f63d229840217a93aae064667/CHANGELOG.txtcnnvd
- https://github.com/nanopb/nanopb/commit/4fe23595732b6f1254cfc11a9b8d6da900b55b0ccnnvd
- https://github.com/nanopb/nanopb/issues/615cnnvd
- https://github.com/nanopb/nanopb/security/advisories/GHSA-85rr-4rh9-hhwhcnnvd
- https://nvd.nist.gov/vuln/detail/CVE-2020-26243cnnvd
- https://www.auscert.org.au/bulletins/ESB-2023.3079cnnvd
- https://www.ibm.com/blogs/psirt/security-bulletin-tensorflow-in-watson-machine-learning-1-6-2-and-1-7-0-has-been-patched-for-a-security-issue-in-nanopb/cnnvd
Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.
Free scan