Security readout for executives and security teams
Plain-English summary
Nanopb can leak memory while decoding a specially formed Protocol Buffers message under narrow conditions. The main business risk is service instability or denial of service in products that parse untrusted protobuf data with vulnerable nanopb versions and dynamic allocation enabled.
Executive priority
Prioritize remediation for internet-facing or externally fed systems that parse protobuf with nanopb. Internal-only systems with trusted inputs are lower urgency, but embedded or vendored copies can be easy to miss and should be inventoried.
Technical view
Before nanopb 0.3.9.7 and 0.4.4, decoding can leak memory when a oneof field contains a static submessage with a dynamic field, and the decoded message repeats that submessage. CVSS 3.1 rates this 7.5, network-accessible, low-complexity, unauthenticated, availability-only impact.
Likely exposure
Exposure is likely limited to systems embedding nanopb versions below 0.3.9.7 or 0.4.0 through 0.4.3, with dynamic allocation enabled, vulnerable schema structure, and untrusted protobuf input. Inventory should include vendored library copies in firmware, agents, services, and third-party components.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation. Public sources describe a specifically formed message causing memory leakage during decoding. The expected impact is availability degradation or denial of service, not data theft or data modification.
Researcher notes
The vulnerable condition is schema- and configuration-dependent, so version matching alone may overstate exposure. Focus validation on dynamic allocation, oneof layout, repeated submessage decoding, and whether attacker-controlled messages can reach the decoder.
Mitigation direction
- Upgrade nanopb to 0.3.9.7, 0.4.4, or later supported releases.
- Set no_unions for affected oneof fields where upgrade is delayed.
- Set the submessage field inside oneof to FT_POINTER where appropriate.
- Use an arena allocator so decoded-message memory can be released afterward.
- Review vendor guidance for downstream products embedding nanopb.
Validation and detection
- Inventory direct, vendored, and transitive nanopb copies and record versions.
- Identify protobuf schemas using oneof static submessages containing dynamic fields.
- Confirm whether dynamic allocation is enabled in affected builds.
- Check whether untrusted protobuf data reaches vulnerable decode paths.
- Verify patched versions or documented workarounds in build artifacts.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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CWE-119: Exact CWE lookup
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Open ATT&CK lookupCWE-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2020-26243 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nanopb/nanopb/security/advisories/GHSA-85rr-4rh9-hhwhCVE reference · x_refsource_CONFIRM
- https://github.com/nanopb/nanopb/issues/615CVE reference · x_refsource_MISC
- https://github.com/nanopb/nanopb/commit/4fe23595732b6f1254cfc11a9b8d6da900b55b0cCVE reference · x_refsource_MISC
- https://github.com/nanopb/nanopb/blob/2b48a361786dfb1f63d229840217a93aae064667/CHANGELOG.txtCVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.