PatchTheCVECVE-2021-3666: body-parser-xml is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype
CVE-2021-3666 is a critical-severity flaw (CVSS 9.8) affecting xml body parser. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
body-parser-xml is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Why this priority
- Critical severity
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.3% (top 30%) |
| CISA exploited list | No |
| Weakness | CWE-1321 |
| Published | 2021-09-13 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-3666?
xml body parser: upgrade to 2.0.3. Exact commands for each OS are on this page.
Is CVE-2021-3666 being exploited?
CVE-2021-3666 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-3666 affect?
CVE-2021-3666 affects xml body parser. Severity is critical (CVSS 9.8). body-parser-xml is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
How urgent is CVE-2021-3666?
Priority 62/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action