CVE-2026-4519

Browser option injection via leading-dash URLs

Published Mar 20, 2026 · Updated Mar 20, 2026

Argument injection in CPython's webbrowser module allows local users to pass browser options through crafted URLs in affected releases. Browser controllers passed URLs beginning with a dash, including after leading whitespace, into browser launch arguments without first rejecting option-like input. Exploitation requires an application to pass attacker-influenced input to webbrowser.open() and user interaction; the resulting behavior depends on the selected browser and injected options.

CVSS severity7.0
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Argument injection in CPython's webbrowser module allows local users to pass browser options through crafted URLs in affected releases. Browser controllers passed URLs beginning with a dash, including after leading whitespace, into browser launch arguments without first rejecting option-like input. Exploitation requires an application to pass attacker-influenced input to webbrowser.open() and user interaction; the resulting behavior depends on the selected browser and injected options.

The record

CVE
CVE-2026-4519
Published
Mar 20, 2026
Updated
Mar 20, 2026
Vendor
Python Software Foundation
Product
CPython
Classifications
CWE-88, CWE-20
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.15.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Python Software Foundation · CPythonversion=0 <3.15.0

Published CVSS scores

3.3NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
7.1Red HatCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L
7.0Python Software FoundationCVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-88Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
CWE-20Improper Input Validation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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