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CVE Record

CVE-2026-4519: webbrowser.open() allows leading dashes in URLs

The webbrowser.open() API would accept leading dashes in the URL which could be handled as command line options for certain web browsers. New behavior rejects leading dashes. Users are recommended to sanitize URLs prior to passing to webbrowser.open().

HighCVSS 7.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Python applications that open attacker-influenced links through webbrowser.open() may pass a leading-dash value to certain browsers as a command-line option instead of a URL. This could affect data confidentiality, integrity, and availability. Exploitation requires user interaction and specific browser handling; remote code execution is not established by the supplied evidence.

Executive priority

Prioritize prompt assessment for desktop tools, automation, and user-facing applications that open externally supplied links. Patch exposed systems through supported vendor channels and add input validation. Systems without attacker-influenced webbrowser.open() inputs are lower priority, but version status should still be confirmed because the supplied affected-range data is incomplete.

Technical view

CVE-2026-4519 is an input-validation and argument-injection weakness in CPython’s webbrowser.open(). Previously, URL values beginning with a dash were accepted and could be interpreted as command-line options by certain browsers. Updated behavior rejects leading dashes. The supplied CVSS 3.1 score is 7.1: network-reachable, high complexity, no privileges, user interaction required.

Likely exposure

Exposure is most likely in applications that pass untrusted or remotely influenced strings directly to webbrowser.open() and launch a browser that interprets leading dashes as options. The supplied version data does not clearly define complete affected or fixed ranges, so deployed Python packages require vendor-specific verification.

Exploitation context

The source bundle does not establish active exploitation, and the CVE is not listed as KEV. Successful abuse depends on attacker control of the opened value, a leading dash, compatible browser behavior, and user interaction. High attack complexity limits broad exploitation, but potential confidentiality and integrity impacts remain significant.

Researcher notes

The weakness maps to CWE-20 and CWE-88. The key trust boundary is between a URL-like application value and the browser process argument list. Researchers should evaluate data flow, browser selection, operating-system launch behavior, and vendor backports without assuming all browsers or CPython packages are exploitable. The supplied sources show multiple patches but do not provide a definitive fixed-version table.

Mitigation direction

  • Install the applicable CPython or operating-system vendor security update after confirming affected package versions.
  • Reject URL inputs beginning with a dash before calling webbrowser.open().
  • Allow only expected URL schemes and trusted input sources.
  • Review Python and Red Hat advisories for platform-specific remediation guidance.

Validation and detection

  • Inventory applications and scripts that call webbrowser.open() or related browser-controller methods.
  • Trace whether users, remote services, documents, or messages can influence values passed to those calls.
  • Confirm deployed Python packages include the vendor correction that rejects leading-dash URLs.
  • Verify application-level validation rejects leading dashes and permits only intended URL schemes.
  • Review browser-launch telemetry for anomalous leading-dash inputs, where such logging exists.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-20: Exact CWE lookup

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cwe · medium confidence lookup

CWE-88: Command execution behavior lookup

Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

Open ATT&CK lookup
cve · low confidence lookup

CVE-2026-4519 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.1 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
3ADP providers
56Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.1CVSS 3.1HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L1.65.5redhat-SADP
7CVSS 4.0HighCVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N——PSF

Vulnerability scoring details

Base CVSS 4.0 score

7High
CVSS 4.0 vector shape for CVE-2026-4519Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPpython: Python: Command-line option injection in webbrowser.open() via crafted URLs
other:Red Hat severity ratingcvssV3_1
  • 2026-03-20T16:02:13.494Z: Reported to Red Hat.
  • 2026-03-20T15:08:32.576Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Python Software FoundationCPython0, 3.11.0, 3.12.0, 3.13.0, 3.14.0, 3.15.0a1unaffected
Weakness

CWE details

CWE-20CWE-88

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.