EUVD-2026-55661Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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
AC:H and UI:R because the victim must obtain a non-default checkout retaining the force-removed commits and actively run npm install; full C/I/A loss as code runs with the developer's privileges.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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
Lifecycle Timeline
2DescriptionCVE.org
use-context-selector is a React useContextSelector hook in userland Between 2026-05-18 15:57:18 and 2026-05-19 15:24:34, the default branch contained malicious commits 9d8481a513b7b0d1c0941b220c69b25de748641b through 6f2dae054ca014068bdbbb4db96006424d674124 that executed remote attacker-controlled code on developer machines during npm install. The commits were removed by force-push, but local clones, forks, and direct-SHA URLs may still contain them, and npm install against an affected checkout will still execute the code today. The package was not published to npm. src/install.js was added and wired into the postinstall script. It fetched a JavaScript payload from an attacker-controlled HTTPS endpoint (configurable via an environment variable), disabled TLS verification, and evaluated the response as code with require available. Execution was deliberately skipped on CI and cloud/serverless environments, targeting developer workstations. The second-stage payload was attacker-hosted and cannot be reconstructed. Assume full compromise of anything reachable from a Node process with the user's permissions. Those who ran npm install against an affected checkout on a developer machine on or after 2026-05-18 15:57:18 should treat the machine as compromised, rotate every credential the machine could reach, audit account activity** since 2026-05-18 15:57:18, and clean local clones.
Articles & Coverage 1
AnalysisAI
Supply-chain compromise of the use-context-selector React library (npm package dai-shi/use-context-selector) planted attacker-controlled malicious code that runs during npm install. Between 2026-05-18 15:57:18 and 2026-05-19 15:24:34 UTC the GitHub default branch carried malicious commits (9d8481a through 6f2dae0) that added src/install.js, wired it into the postinstall hook, fetched a second-stage JavaScript payload from an attacker HTTPS endpoint with TLS verification disabled, and evaluated it with require available - but only on developer workstations (execution was deliberately skipped on CI and cloud/serverless). …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires obtaining and installing a git checkout that still contains the malicious commits 9d8481a…748641b through 6f2dae0…674124 - specifically a local clone, fork, mirror, or direct-commit-SHA URL captured while the default branch was poisoned (2026-05-18 15:57:18 to 2026-05-19 15:24:34 UTC) - and then running `npm install` (or any install that triggers the `postinstall` hook) against it. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine high-priority event, not a paper-high-CVSS issue, but its real-world blast radius is bounded by an unusual delivery path. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | The malicious commits were already removed from the upstream default branch by force-push (upstream fix available via git history rewrite; no tagged patched release version is applicable since the package was never published compromised), so the primary action is to purge affected checkouts rather than upgrade a version number: delete and re-clone any local clone/fork of dai-shi/use-context-selector, or `git fetch` and hard-reset to the current clean default branch, and verify that `src/install.js` and any `postinstall` entry referencing it are absent from package.json before installing. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify and isolate developer workstations that performed git clone or npm install on dai-shi/use-context-selector between May 18-19, 2026 (commits 9d8481a-6f2dae0), audit system logs for src/install.js execution or HTTPS connections to attacker endpoints, and rotate all credentials held by affected developers. …
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External POC / Exploit Code
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