Mojic: Observable Timing Discrepancy in HMAC Verification

Exploitation

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

CVSS

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

EPSS

• CVE-2026-41244: 0.11% estimated exploitation activity in the next 30 days; percentile 1.20 (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.

Summary The CipherEngine in Mojic v2.1.3 uses a standard equality operator (!==) to verify the HMAC-SHA256 integrity seal during the decryption phase. This creates an Observable Timing Discrepancy (CWE-208), allowing a potential attacker to bypass the file integrity check via a timing attack. Details In lib/CipherEngine.js, the footer check validates the HMAC signature using a standard string comparison: if (footerHex !== calcDigest) { ... } Standard string comparisons in JavaScript short-circuit; they return false the moment a character mismatch occurs. Because the time taken to evaluate the comparison is proportional to the number of matching leading bytes, an attacker can measure the exact microseconds it takes for the engine to throw the FILETAMPERED error. By repeatedly altering the signature byte-by-byte and analyzing these minute timing differences, a malicious actor can theoretically forge a valid HMAC signature without possessing the decryption password. PoC The vulnerable…

Published by the source

16 Apr 2026, 21:10 UTC

Last modified by the source

5 May 2026, 16:26 UTC

Source last checked

26 Oct 2026, 12:51 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wqq3-wfmp-v85g

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-wqq3-wfmp-v85g

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# Patch Next advisory brief: CVE-2026-41244

Advisory: Mojic: Observable Timing Discrepancy in HMAC Verification
IDs: CVE-2026-41244, GHSA-wqq3-wfmp-v85g
Record: https://patchnext.com/advisories/cve-2026-41244 (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 4.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mojic 2.1.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm mojic: affected <= 2.1.3; fixed in 2.1.4

## Suggested inspection (read-only)
- `npm ls mojic --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 mojic.
- 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-wqq3-wfmp-v85g (OSV record GHSA-wqq3-wfmp-v85g lists affected ranges: npm mojic >=0 <2.1.4 (fixed))
- Verified: https://github.com/advisories/GHSA-wqq3-wfmp-v85g (GitHub-reviewed advisory GHSA-wqq3-wfmp-v85g lists affected ranges: npm mojic >=0 <=2.1.3)

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