CVE-2021-3177 / Siemens SSA-398330: n/a — Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Distribution release	Source package	Vendor state	Fixed version	Evidence
Alpine v3.23v3.23 · main	`python3`	Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.	`3.8.7-r2`	Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.22v3.22 · main	`python3`	Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.	`3.8.7-r2`	Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.21v3.21 · main	`python3`	Vendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.	`3.8.7-r2`	Alpine Security Database ↗Source updated 3 Oct 2026

Recommended actionPatch only the product branches with a verified fix

Critical technical impact with a remotely reachable, unauthenticated path and a public exploit reference; no CISA KEV confirmation is currently recorded. Verified remediation exists for at least one product or source, but 5 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product

What, why and how

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.

What

Why

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may execute code or commands in the affected security context.

What

Why

The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.

How

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material

Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.

Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path: a network path → Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') → execute code or commands in the affected security context
Attack surface: Network
Privileges required: None: unauthenticated exploitation is possible
User interaction: None
Attack complexity: Low: no specialised conditions are recorded
Security boundary: Unchanged: impact remains within the vulnerable component's security authority
Weakness ? CWE means Common Weakness Enumeration: a standard category for the underlying weakness.: CWE-120 ↗
CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow'). The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
CVSS vector ? CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land: After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.

NetworkUnauthenticatedRemote code executionCWE-120Public exploit reference

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2021-26520Official EUVD mapping

0 linked advisory records.

Official EUVD record ↗

BSI · German · WID-SEC-2022-0495Python: Schwachstelle ermöglicht Ausführen von beliebigem Programmcode mit Benutzerrechten

Ein entfernter, anonymer Angreifer kann eine Schwachstelle in Python ausnutzen, um beliebigen Programmcode mit Benutzerrechten auszuführen.

n/a — Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

Evidence used

Compensating controls

Verification

Remediation availability differs by product scope

EUVD-2021-26520

What, why and how

Exploit reality and attack path

Official authority intelligence

Patch and workaround

Evidence and provenance