CVE-2021-3121
CVE-2021-3121 is a high-severity vulnerability in Golang Protobuf with a CVSS 3.x base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-129.
Key facts
- Severity: High (CVSS 3.x base score 8.6)
- CVSS v2: 7.5
- EPSS exploit prediction: 3% (88th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-129
- Affected product: Golang Protobuf
- Published:
- Last modified:
Description
An issue was discovered in GoGo Protobuf before 1.3.2. plugin/unmarshal/unmarshal.go lacks certain index validation, aka the "skippy peanut butter" issue.
Frequently asked questions
- What is CVE-2021-3121?
- An issue was discovered in GoGo Protobuf before 1.3.2. plugin/unmarshal/unmarshal.go lacks certain index validation, aka the "skippy peanut butter" issue.
- How severe is CVE-2021-3121?
- CVE-2021-3121 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability high.
- Is CVE-2021-3121 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (88th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2021-3121?
- CVE-2021-3121 primarily affects Golang Protobuf. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2021-3121?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2021-3121 published?
- CVE-2021-3121 was published on 2021-01-11 and last updated on 2026-06-17.
References
- https://discuss.hashicorp.com/t/hcsec-2021-23-consul-exposed-to-denial-of-service-in-gogo-protobuf-dependency/29025
- https://github.com/gogo/protobuf/commit/b03c65ea87cdc3521ede29f62fe3ce239267c1bc
- https://github.com/gogo/protobuf/compare/v1.3.1...v1.3.2
- https://lists.apache.org/thread.html/r68032132c0399c29d6cdc7bd44918535da54060a10a12b1591328bff%40%3Cnotifications.skywalking.apache.org%3E
- https://lists.apache.org/thread.html/r88d69555cb74a129a7bf84838073b61259b4a3830190e05a3b87994e%40%3Ccommits.pulsar.apache.org%3E
- https://lists.apache.org/thread.html/rc1e9ff22c5641d73701ba56362fb867d40ed287cca000b131dcf4a44%40%3Ccommits.pulsar.apache.org%3E
- https://security.netapp.com/advisory/ntap-20210219-0006/
Affected products (3)
- cpe:2.3:a:golang:protobuf:*:*:*:*:*:*:*:*
- cpe:2.3:a:hashicorp:consul:*:*:*:*:-:*:*:*
- cpe:2.3:a:hashicorp:consul:*:*:*:*:enterprise:*:*:*
Other CWE-129 (Improper Validation of Array Index) vulnerabilities
- CVE-2020-27485 — Critical (CVSS 9.9): Garmin Forerunner 235 before 8.20 is affected by: Array index error. The component is: ConnectIQ TVM. The attack vector…
- CVE-2020-27483 — Critical (CVSS 9.9): Garmin Forerunner 235 before 8.20 is affected by: Array index error. The component is: ConnectIQ TVM. The attack vector…
- CVE-2026-21413 — Critical (CVSS 9.8): A heap-based buffer overflow vulnerability exists in the lossless_jpeg_load_raw functionality of LibRaw Commit 0b56545…
- CVE-2025-27034 — Critical (CVSS 9.8): Memory corruption while selecting the PLMN from SOR failed list.
- CVE-2025-3357 — Critical (CVSS 9.8): IBM Tivoli Monitoring 6.3.0.7 through 6.3.0.7 Service Pack 19 could allow a remote attacker to execute arbitrary code…
- CVE-2024-45569 — Critical (CVSS 9.8): Memory corruption while parsing the ML IE due to invalid frame content.
Browse all CWE-129 (Improper Validation of Array Index) vulnerabilities →