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CVE-2021-21401

22
FAUCET Score

CVE-2021-21401 is a vulnerability in Nanopb, a Protocol Buffers implementation in C, affecting versions prior to 0.3.9.8 and 0.4.5. Specifically, a malformed message containing an 'oneof' field with both pointer and non-pointer fields can lead to invalid free() or realloc() calls, potentially causing memory corruption. Rated as High severity (CVSS 7.1), this vulnerability can be triggered remotely with low attack complexity and no user interaction, potentially leading to data integrity compromise (I:H) and availability impact (A:L). There is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.3.9.8CPE matchmatch criteria
cpe:2.3:a:nanopb_project:nanopb:*:*:*:*:*:*:*:*
>= 0.4.0, < 0.4.5CPE matchmatch criteria
cpe:2.3:a:nanopb_project:nanopb:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.1HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
HIGH
Availability Impact
LOW
Exploitability Score
2.8
Impact Score
4.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.81%
Probability of exploitation in next 30 days
EPSS Percentile
76.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0181 is in the 74th percentile among its peer group of 17,844 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: nanopbFixed in: 0.3.9.8
pippatch availablevia ghsa
Product: nanopbFixed in: 0.4.5

Vendor Advisories (1)

pipGHSA-7mv5-5mxh-qg88high

nanopb vulnerable to invalid free() call with oneofs and PB_ENABLE_MALLOC

Aug 30, 2024

References

github.com / nanopb/nanopb/blob/c9124132a604047d0ef97a09c0e99cd9bed2c818/CHANGELOG.txt
Release NotesThird Party Advisory
github.com / nanopb/nanopb/commit/e2f0ccf939d9f82931d085acb6df8e9a182a4261
PatchThird Party Advisory
github.com / nanopb/nanopb/issues/647
ExploitIssue TrackingThird Party Advisory
github.com / nanopb/nanopb/security/advisories/GHSA-7mv5-5mxh-qg88
ExploitPatchThird Party Advisory