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Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2021-3177

CVE-2021-3177CRITICAL
n/a n/a — Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain P…
  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  U  H  H  H    9.8   .2422   97.8     —
AFFECTED
  Product  Versions  Fixed
  n/a      n/a –     —
TIMELINE
  Jan 19  Reserved by mitre
  Jan 19  Published (CNA: mitre)
  Oct 14  EXPLOIT PUBLISHED — CVE-2021-3177. Public exploit reference added.
CWE-120 · CNA: mitre · CVSS v3.1 · 29 references · NVD status: Modified

Description

Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely.

Lifecycle

Complete event history — 3 events, chronological
DateEventDetail
January 19, 2021ReservedReserved by mitre
January 19, 2021PublishedPublished (CNA: mitre)
October 14, 2026EXPLOIT PUBLISHEDEXPLOIT PUBLISHED — CVE-2021-3177. Public exploit reference added.

Affected

Affected products and packages — 1 row
VendorProduct / PackageEcosystemVersion introducedFixed
n/an/a—n/a—

Weaknesses

CWE-120

References (29)

Related

Authoritative record: CVE-2021-3177 at cve.org

Weaknesses: CWE-120

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-3177 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.