CVE-2026-31900
Black is the uncompromising Python code formatter. Black provides a GitHub action for formatting code. This action supports an option, use_pyproject: true, for reading the version of Black to use from the repository pyproject.toml. A malicious pull request could edit pyproject.toml to use a direct URL reference to a malicious repository. This could lead to arbitrary code execution in the context of the GitHub Action. Attackers could then gain access to secrets or permissions available in the context of the action. Version 26.3.0 fixes this vulnerability.
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exploitation prediction scoring system. probability this vulnerability will be exploited in the wild in the next 30 days.
cvss
common vulnerability scoring system v3.1. measures intrinsic severity on a 0-10 scale.
epss
0.0018
kev
no
cisa known exploited vulnerabilities catalog. confirmed active exploitation.
CVSS 3.1
Common Vulnerability Scoring System v3.1
9.8
/ 10
CRITICAL
exploitability
Attack Vector
Network
Attack Vector (AV:N): exploitable remotely over the network — most dangerous. no physical or adjacent access needed.
Attack Complexity
Low
Attack Complexity (AC:L): no special conditions needed. attack can be reliably reproduced.
Privileges Required
None
Privileges Required (PR:N): no authentication needed. any anonymous attacker can exploit this.
User Interaction
None
User Interaction (UI:N): no victim action needed. fully exploitable without user interaction.
impact
Scope
Unchanged
Scope (S:U): impact limited to the vulnerable component.
Confidentiality
High
Confidentiality (C:H): total information disclosure. attacker gains access to all data within the component.
Integrity
High
Integrity (I:H): complete data modification possible. attacker can modify any data.
Availability
High
Availability (A:H): total denial of service. attacker can fully shut down the resource.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 4.0
Common Vulnerability Scoring System v4.0
8.7
/ 10
HIGH
exploitability
Attack Vector
Network
Attack Vector (AV:N): exploitable remotely over the network — most dangerous. no physical or adjacent access needed.
Attack Complexity
Low
Attack Complexity (AC:L): no special conditions needed. attack can be reliably reproduced.
Attack Requirements
None
Attack Requirements (AT:N): no special deployment or execution conditions needed.
Privileges Required
Low
Privileges Required (PR:L): requires basic user-level access.
User Interaction
None
User Interaction (UI:N): no victim action needed. fully exploitable without user interaction.
vulnerable system impact
Vuln Confidentiality
High
Confidentiality (VC:H): total information disclosure. attacker gains access to all data within the component.
Vuln Integrity
High
Integrity (VI:H): complete data modification possible. attacker can modify any data.
Vuln Availability
High
Availability (VA:H): total denial of service. attacker can fully shut down the resource.
subsequent system impact
Sub Confidentiality
None
Subsequent Confidentiality: impact on data confidentiality of downstream/connected systems. Value: N (None)
Sub Integrity
None
Subsequent Integrity: impact on data integrity of downstream/connected systems. Value: N (None)
Sub Availability
None
Subsequent Availability: impact on service availability of downstream/connected systems. Value: N (None)
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
activity density
rdintel assessment
flagged malicious repos detected. do not execute.
public exploit available. prioritize patching.
composite score from 15+ signals including exploitation status, epss probability, detection coverage, and community attention. 0-100 scale.
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