Incorrect Calculation in the MSR JavaScript Cryptography Library

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2020-1026: 2.60% estimated exploitation activity in the next 30 days; percentile 85.40 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

A Security Feature Bypass vulnerability exists in the MSR JavaScript Cryptography Library that is caused by multiple bugs in the library's Elliptic Curve Cryptography (ECC) implementation.An attacker could potentially abuse these bugs to learn information about a server's private ECC key (a key leakage attack) or craft an invalid ECDSA signature that nevertheless passes as valid.The security update addresses the vulnerability by fixing the bugs disclosed in the ECC implementation, aka MSR JavaScript Cryptography Library Security Feature Bypass Vulnerability.

Published by the source

6 Jan 2022, 19:44 UTC

Last modified by the source

8 Nov 2023, 04:01 UTC

Source last checked

26 Oct 2026, 12:21 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9x9j-836w-8f55

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9x9j-836w-8f55

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# Patch Next advisory brief: CVE-2020-1026

Advisory: Incorrect Calculation in the MSR JavaScript Cryptography Library
IDs: CVE-2020-1026, GHSA-9x9j-836w-8f55
Record: https://patchnext.com/advisories/cve-2020-1026 (revision 2, source checked 26 Oct 2026, 12:21 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: msrcrypto 1.5.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm msrcrypto: affected < 1.5.8; fixed in 1.5.8

## Suggested inspection (read-only)
- `npm ls msrcrypto --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 msrcrypto.
- 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-9x9j-836w-8f55 (OSV record GHSA-9x9j-836w-8f55 lists affected ranges: npm msrcrypto >=0 <1.5.8 (fixed))
- Verified: https://github.com/advisories/GHSA-9x9j-836w-8f55 (GitHub-reviewed advisory GHSA-9x9j-836w-8f55 lists affected ranges: npm msrcrypto >=0 <1.5.8)

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