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Medium, CVSS 5.2amended

Evolver has Prototype Pollution via Object.assign() in its mailbox store operations

CVE-2026-42077GHSA-2cjr-5v3h-v2w4

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@evomap/evolver 1.69.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.2 · CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H
EPSS
  • CVE-2026-42077: 0.16% estimated exploitation activity in the next 30 days; percentile 4.91 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary A prototype pollution vulnerability in the mailbox store module allows attackers to modify the behavior of all JavaScript objects by injecting malicious properties into Object.prototype. The vulnerability exists in the applyUpdate() and updateRecord() functions which use Object.assign() to merge user-controlled data without filtering dangerous keys like proto, constructor, or prototype. Details The vulnerability exists in src/proxy/mailbox/store.js at lines 123 and 145: The vulnerability can be triggered when an attacker has the ability to write to the messages.jsonl file (used for mailbox persistence). By crafting a malicious JSONL entry with proto as a field key, the attacker can pollute the prototype of all objects. The data flows from: 1. messages.jsonl file → 2. readLines() function (line 47) → 3. rebuildIndex() (line 113) → applyUpdate() (line 121) → 4. Object.assign() pollutes prototype PoC Prerequisites: - Node.js installed - Access to write to the mailbox messages…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-2cjr-5v3h-v2w4

  2. Revision 1 · created ·

    Published from osv record GHSA-2cjr-5v3h-v2w4

Agent brief

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# Patch Next advisory brief: CVE-2026-42077

Advisory: Evolver has Prototype Pollution via `Object.assign()` in its mailbox store operations
IDs: CVE-2026-42077, GHSA-2cjr-5v3h-v2w4
Record: https://patchnext.com/advisories/cve-2026-42077 (revision 2, source checked 26 Oct 2026, 12:51 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @evomap/evolver 1.69.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @evomap/evolver: affected < 1.69.3; fixed in 1.69.3

## Suggested inspection (read-only)
- `npm ls @evomap/evolver --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @evomap/evolver.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-2cjr-5v3h-v2w4 (OSV record GHSA-2cjr-5v3h-v2w4 lists affected ranges: npm @evomap/evolver >=0 <1.69.3 (fixed))
- Verified: https://github.com/advisories/GHSA-2cjr-5v3h-v2w4 (GitHub-reviewed advisory GHSA-2cjr-5v3h-v2w4 lists affected ranges: npm @evomap/evolver >=0 <1.69.3)

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