How severe is CVE-2026-34778?

CVE-2026-34778 has a CVSS score of 5.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-34778?

CVE-2026-34778 affects the following packages: electron (npm), electron (npm), electron (npm), electron (npm). Ecosystems affected: npm.

How do I fix CVE-2026-34778?

Update electron to 38.8.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34778 is resolved across your whole dependency graph.

How do I detect CVE-2026-34778 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for electron, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-34778 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-34778 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34778 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-34778?

CVE-2026-34778 has an EPSS (Exploit Prediction Scoring System) score of 0.1%, placing it in the 3th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-34778?

CVE-2026-34778 is classified as CWE-290 (CWE-290), CWE-345 (CWE-345). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-34778 published, and has it been updated?

CVE-2026-34778 was published on April 3, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

CVE-2026-34778 — electron

MEDIUM

CVE-2026-34778 is a medium-severity (CVSS 5.9) CWE-290 vulnerability in electron. A fix is available for electron — see the affected versions and patch details below.

Electron: Service worker can spoof executeJavaScript IPC replies

Also known asGHSA-xj5x-m3f3-5x3h

Published

Apr 3, 2026

Updated

Oct 28, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-34778.

EPSS Exploitation Probability

via FIRST.org ↗

0.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs3th percentile — riskier than 3% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

4 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

2Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream

electronnpm

12.2Mdownloads / week

Description

Impact

A service worker running in a session could spoof reply messages on the internal IPC channel used by webContents.executeJavaScript() and related methods, causing the main-process promise to resolve with attacker-controlled data.

Apps are only affected if they have service workers registered and use the result of webContents.executeJavaScript() (or webFrameMain.executeJavaScript()) in security-sensitive decisions.

Workarounds

Do not trust the return value of webContents.executeJavaScript() for security decisions. Use dedicated, validated IPC channels for security-relevant communication with renderers.

Fixed Versions

41.0.0
40.8.1
39.8.1
38.8.6

For more information

If there are any questions or comments about this advisory, please email [email protected]

Affected Packages

4 total 4 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`electron`	all versions	38.8.6`npm install electron@38.8.6`
📦npm	`electron`	≥ 39.0.0-alpha.1&&< 39.8.1	39.8.1`npm install electron@39.8.1`
📦npm	`electron`	≥ 40.0.0-alpha.1&&< 40.8.1	40.8.1`npm install electron@40.8.1`
📦npm	`electron`	≥ 41.0.0-alpha.1&&< 41.0.0	41.0.0`npm install electron@41.0.0`

Affected Products

1 product · 17 configurations

Application

electronelectronjs

≥ 40.0.0 && < 40.8.1

1 version

41.0.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for electron, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update electron to 38.8.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34778 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2026-34778 (CC BY 4.0)

Frequently Asked Questions

### Impact A service worker running in a session could spoof reply messages on the internal IPC channel used by `webContents.executeJavaScript()` and related methods, causing the main-process promise to resolve with attacker-controlled data. Apps are only affected if they have service workers registered and use the result of `webContents.executeJavaScript()` (or `webFrameMain.executeJavaScript()`) in security-sensitive decisions. ### Workarounds Do not trust the return value of `webContents.executeJavaScript()` for security decisions. Use dedicated, validated IPC channels for security-releva