Mitigation bypass in the DOM: Copy & Paste and Drag & Drop component
Mitigation bypass in the DOM: Copy & Paste and Drag & Drop component. This vulnerability was fixed in Firefox 156, Firefox ESR 140.16, Firefox ESR 153.3, Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.
- Published
- Sep 15, 2026
- Updated
- Sep 21, 2026
- EPSS
- 0.2% · 14th percentile
- CWE
- CWE-693
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Report tools
Action score
21
Monitor
Low priority for now.
- CVSS
- 21 / 40 · 5.4 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
Affected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (mozilla). Independent of NVD's CPE analysis and usually ahead of it.
Mozilla Firefox
- 140.16 and later · up to and including 140.*not affected · rpm
- 153.3 and later · up to and including 153.*not affected · rpm
- 156 and laternot affected · rpm
Mozilla Thunderbird
- 140.16 and later · up to and including 140.*not affected · rpm
- 153.3 and later · up to and including 153.*not affected · rpm
- 156 and laternot affected · rpm
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | firefox-esr | before 140.16.0esr-1~deb12u1 | 140.16.0esr-1~deb12u1 |
| Debian:12 | thunderbird | before 1:140.16.0esr-1~deb12u1 | 1:140.16.0esr-1~deb12u1 |
| Debian:13 | firefox-esr | before 140.16.0esr-1~deb13u1 | 140.16.0esr-1~deb13u1 |
| Debian:13 | thunderbird | before 1:140.16.0esr-1~deb13u1 | 1:140.16.0esr-1~deb13u1 |
| Debian:14 | firefox-esr | before 140.16.0esr-1 | 140.16.0esr-1 |
| Debian:14 | thunderbird | all versions | — |
Same product
mozilla: all recordsOther highest-scoring records for the same primary product.
- CVE-2010-3765Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before 3.1.6 and 3.0.x before 3.0.10, and SeaMonkey 2.x befKEV94Now
- CVE-2019-11708Insufficient vetting of parameters passed with the Prompt:Open IPC message between child and parent processes can result in the non-sandboxeKEV87Now
- CVE-2015-4495The PDF reader in Mozilla Firefox before 39.0.3, Firefox ESR 38.x before 38.1.1, and Firefox OS before 2.2 allows remote attackers to bypassKEV86Now
- CVE-2013-1690Mozilla Firefox before 22.0, Firefox ESR 17.x before 17.0.7, Thunderbird before 17.0.7, and Thunderbird ESR 17.x before 17.0.7 do not properKEV86Now
- CVE-2019-17026Incorrect alias information in IonMonkey JIT compiler for setting array elements could lead to a type confusion.KEV79This week
- CVE-2024-9680An attacker was able to achieve code execution in the content process by exploiting a use-after-free in Animation timelines.KEV76This week
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:firefox-esr | 140.16.0esr-1~deb12u1 · Debian:12 | Package registry (OSV) |
| debian:thunderbird | 1:140.16.0esr-1~deb12u1 · Debian:12 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2026-7587428 days apartSandbox escape in the Remote Settings Client component40Plan
- CVE-2026-2761203 days apartSandbox escape in the Graphics: WebRender component40Plan
- CVE-2026-920660 days apartSandbox escape in the Profile Backup component39Monitor
- CVE-2026-1638256 days apartMitigation bypass in the DOM: Service Workers component39Monitor
- CVE-2026-1638356 days apartMitigation bypass in the DOM: Networking component39Monitor
- CVE-2026-1638856 days apartSandbox escape in the DOM: Networking component39Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- A user must open a link or visit a page.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- low · data can be read
- Integrity
- low · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- Low
- Availability impact
- None
Weakness class (CWE)
CWE-693 · Protection Mechanism FailureCVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Accessing Functionality Not Properly Constrained by ACLsCAPEC-1likelihood: High · High
- Cross Site TracingCAPEC-107likelihood: Medium · Very High
- Directory IndexingCAPEC-127likelihood: High · Medium
- Using Malicious FilesCAPEC-17likelihood: High · Very High
- Encryption Brute ForcingCAPEC-20likelihood: Low · Low
- Exploiting Trust in ClientCAPEC-22likelihood: High · High
- Escaping a Sandbox by Calling Code in Another LanguageCAPEC-237likelihood: Low · Very High
- Using Unpublished Interfaces or FunctionalityCAPEC-36likelihood: Medium · High
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- bugzilla.mozilla.org/show_bug.cgi?id=2058417
- www.mozilla.org/security/advisories/mfsa2026-90/
- www.mozilla.org/security/advisories/mfsa2026-92/
- www.mozilla.org/security/advisories/mfsa2026-93/
- www.mozilla.org/security/advisories/mfsa2026-94/
- www.mozilla.org/security/advisories/mfsa2026-95/
- www.mozilla.org/security/advisories/mfsa2026-96/
Vendor advisories and official records. Exploit/PoC links are deliberately left out.