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GHSA-85rr-4rh9-hhwh

HighCVSS 7.5 / 10
Published Nov 25, 2020·Last modified Mar 13, 2026
Affected Components(0)

No affected components available

Description

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.

Risk Scores
Base Score
7.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.

Threat Intelligence
6.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
2.61%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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