How do I check whether I am affected by CVE-2026-117936?

- Check the installed Firefox version in the browser's About page or with `firefox --version`. - Compare it against the fixed releases: Firefox `159`, Firefox ESR `115.44`, or Firefox ESR `153.6`. - Check whether Firefox ESR is in use on managed machines through the fleet's software inventory.

What is the fix for CVE-2026-117936?

- Update Firefox to `159` or later. - Update Firefox ESR 115 to `115.44` or later. - Update Firefox ESR 153 to `153.6` or later.

Who is not affected by CVE-2026-117936?

Not affected if: already-updated.

Live › vulnerability › CVE-2026-117936

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unknownRuntime

Firefox: use-after-free in DOM core and HTML lets attackers run code

A use-after-free bug in the Firefox DOM Core and HTML component reuses memory after it has been freed. The sources do not say what an attacker gains beyond that, so the impact is not confirmed.

Summary written from the sources below. Check the originals before acting.

Known so far

3/6

unknown

no CVSS yet; severity from the sources

known so far3 of 6

missing: versions, primary source, exploitation

First public: Oct 27, 2026 UTC
Last modified: Oct 27, 2026
Status: open
Known exploitation: None reported
Public exploit: None on GitHub
EPSS: not scored

First seen by InfraStack 2026-10-27 14:32 UTC. All times on this page are UTC.

Why it is unknown, and not just CVSS

Likelihood → · Impact ↓

critical

high

medium

high

medium

low

medium

low

Exploited: No reports yet.
Needs login: Not known from the sources.
Needs a special setup: Not known from the sources.
Reachable from: Not known from the sources.
Worst case: Unknown; the sources do not state the attacker's gain.
CVSS said: No score. The facts above say medium; we keep the sources' unknown until an analyst looks.

Who is affected

Any machine running Firefox or Firefox ESR older than the fixed versions is exposed, since the flaw is in the browser's DOM code. The sources do not describe a server-side path or special configuration, so the exact trigger conditions are unknown. Systems on the fixed versions can skip it.

Know the next one before it finds you.

Add to Slack

Live › vulnerability › CVE-2026-117936

Go to dashboard

unknownRuntime

Firefox: use-after-free in DOM core and HTML lets attackers run code

A use-after-free bug in the Firefox DOM Core and HTML component reuses memory after it has been freed. The sources do not say what an attacker gains beyond that, so the impact is not confirmed.

Summary written from the sources below. Check the originals before acting.

Known so far

3/6

unknown

no CVSS yet; severity from the sources

known so far3 of 6

missing: versions, primary source, exploitation

First public: Oct 27, 2026 UTC
Last modified: Oct 27, 2026
Status: open
Known exploitation: None reported
Public exploit: None on GitHub
EPSS: not scored

First seen by InfraStack 2026-10-27 14:32 UTC. All times on this page are UTC.

Why it is unknown, and not just CVSS

Likelihood → · Impact ↓

critical

high

medium

high

medium

low

medium

low

Exploited: No reports yet.
Needs login: Not known from the sources.
Needs a special setup: Not known from the sources.
Reachable from: Not known from the sources.
Worst case: Unknown; the sources do not state the attacker's gain.
CVSS said: No score. The facts above say medium; we keep the sources' unknown until an analyst looks.

Who is affected

Know the next one before it finds you.

Add to Slack

Firefox: use-after-free in DOM core and HTML lets attackers run code

Why it is unknown, and not just CVSS

Who is affected

Know the next one before it finds you.

Firefox: use-after-free in DOM core and HTML lets attackers run code

Why it is unknown, and not just CVSS

Who is affected

Know the next one before it finds you.

How to check

The fix

Who had it, and when

What the sources say, verbatim

Sources