GHSA-7mv5-5mxh-qg88
HIGHnanopb vulnerable to invalid free() call with oneofs and PB_ENABLE_MALLOC
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
nanopb🐍nanopbReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | nanopb | ≥ 0.3.2&&< 0.3.9.8 | 0.3.9.8 |
| 🐍PyPI | nanopb | ≥ 0.4.0&&< 0.4.5 | 0.4.5 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nanopb. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update nanopb to 0.3.9.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-7mv5-5mxh-qg88 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-7mv5-5mxh-qg88 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-7mv5-5mxh-qg88. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-7mv5-5mxh-qg88 in your dependencies?
O3 detects GHSA-7mv5-5mxh-qg88 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.