CVE-2021-21401

Description

Nanopb is a small code-size Protocol Buffers implementation in ansi C. In Nanopb before versions 0.3.9.8 and 0.4.5, 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. This has been fixed in versions 0.3.9.8 and 0.4.5. See referenced GitHub Security Advisory for more information including workarounds.

How to fix CVE-2021-21401

To remediate CVE-2021-21401, upgrade the affected package to a fixed version below.

• —upgrade to 0.4.4-2 or later
• —upgrade to 0.3.9.8 or later
• —upgrade to e2f0ccf939d9f82931d085acb6df8e9a182a4261 or later

Is CVE-2021-21401 being exploited?

Low — EPSS is 0.8%, meaning exploitation activity has not been observed at scale.

Affected packages (3)

• from 0, < 0.4.4-2
• >= 0.3.2, < 0.3.9.8
• from 0, < e2f0ccf939d9f82931d085acb6df8e9a182a4261 | from 0, < 0.3.9.8, >= 0.4.0, < 0.4.5

CVSS scores

References (9)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2021-21401
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2021-21401
• PATCHgithub.com/nanopb/nanopb
• WEBgithub.com/nanopb/nanopb/blob/c9124132a604047d0ef97a09c0e99cd9bed2c818/CHANGELOG.txt#L1