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GHSA-7mv5-5mxh-qg88
No affected components available
Impact
Decoding a specifically formed message can cause invalid free() or realloc() calls if the message type contains an oneof field, and the oneof directly contains both a pointer field and a non-pointer field. If the message data first contains the non-pointer field and then the pointer field, the data of the non-pointer field is incorrectly treated as if it was a pointer value. Such message data rarely occurs in normal messages, but it is a concern when untrusted data is parsed.
Patches
Preliminary patch is available on git for 0.4.x and 0.3.x branches. The fix will be released in versions 0.3.9.8 and 0.4.5 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 all fields inside the oneof to
FT_POINTER. This ensures that the data contained inside theunionis always a valid pointer. - Heap implementations that guard against invalid
free()provide a partial mitigation. Depending on the message type, the pointer value may be attacker controlled and can be used to bypass heap protections.
References
Bug report: https://github.com/nanopb/nanopb/issues/647
For more information
If you have any questions or comments about this advisory, comment on the bug report linked above.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. 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 integrity of the data. There is a low impact on the availability of the system.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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