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CVE-2025-6435· NVD / CVE Program· CNA mozilla

Save as in Devtools could download files without sanitizing the extension

Noroxi assessment

Priority: Monitor (action score 32/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.45% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: firefox-esr (openSUSE:Tumbleweed) 140.1.0-1.1; MozillaFirefox (openSUSE:Tumbleweed) 140.0.2-1.1; MozillaThunderbird (openSUSE:Tumbleweed) 140.1.0-1.1.

Low priority for now. Upgrade to firefox-esr (openSUSE:Tumbleweed) 140.1.0-1.1; MozillaFirefox (openSUSE:Tumbleweed) 140.0.2-1.1; MozillaThunderbird (openSUSE:Tumbleweed) 140.1.0-1.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

If a user saved a response from the Network tab in Devtools using the Save As context menu option, that file may not have been saved with the `.download` file extension. This could have led to the user inadvertently running a malicious executable. This vulnerability was fixed in Firefox 140 and Thunderbird 140.

HighCVSS 8.1 · v3.1—No exploit Fix available
Published
Jun 24, 2025
Updated
Sep 30, 2026
EPSS
0.4% · 38th percentile

Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
32 / 40 · 8.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2025-6435

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
mozillafirefox
mozillathunderbird

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • mozilla firefoxbefore 140.0
  • mozilla thunderbirdbefore 140.0

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 and laternot affected · rpm

  • Mozilla Thunderbird

    • 140 and laternot affected · rpm

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
openSUSE:Tumbleweedfirefox-esrbefore 140.1.0-1.1140.1.0-1.1
openSUSE:TumbleweedMozillaFirefoxbefore 140.0.2-1.1140.0.2-1.1
openSUSE:TumbleweedMozillaThunderbirdbefore 140.1.0-1.1140.1.0-1.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSpipewirebefore 0.3.24-150300.4.8.10.3.24-150300.4.8.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSpipewirebefore 0.3.24-150300.4.8.10.3.24-150300.4.8.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSxdg-desktop-portalbefore 1.8.0-150200.5.8.11.8.0-150200.5.8.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSxdg-desktop-portalbefore 1.8.0-150200.5.8.11.8.0-150200.5.8.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSpipewirebefore 0.3.49-150400.3.7.10.3.49-150400.3.7.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSpipewirebefore 0.3.49-150400.3.7.10.3.49-150400.3.7.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSxdg-desktop-portalbefore 1.10.1-150400.3.8.11.10.1-150400.3.8.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSxdg-desktop-portalbefore 1.10.1-150400.3.8.11.10.1-150400.3.8.1
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSpipewirebefore 0.3.64-150500.3.7.20.3.64-150500.3.7.2
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSpipewirebefore 0.3.64-150500.3.7.20.3.64-150500.3.7.2
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSxdg-desktop-portalbefore 1.16.0-150500.3.8.11.16.0-150500.3.8.1
SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOSxdg-desktop-portalbefore 1.16.0-150500.3.8.11.16.0-150500.3.8.1
SUSE:Linux Enterprise Module for Desktop Applications 15 SP6MozillaFirefoxbefore 140.1.0-150200.152.193.1140.1.0-150200.152.193.1
SUSE:Linux Enterprise Module for Desktop Applications 15 SP6MozillaFirefoxbefore 140.1.0-150200.152.193.1140.1.0-150200.152.193.1
SUSE:Linux Enterprise Module for Desktop Applications 15 SP6MozillaFirefox-branding-SLEbefore 140-150200.9.21.1140-150200.9.21.1
SUSE:Linux Enterprise Module for Desktop Applications 15 SP6MozillaFirefox-branding-SLEbefore 140-150200.9.21.1140-150200.9.21.1
SUSE:Linux Enterprise Module for Package Hub 15 SP6MozillaThunderbirdbefore 140.1.0-150200.8.230.1140.1.0-150200.8.230.1
SUSE:Linux Enterprise Module for Package Hub 15 SP6MozillaThunderbirdbefore 140.1.0-150200.8.230.1140.1.0-150200.8.230.1
SUSE:Linux Enterprise Module for Package Hub 15 SP6pipewirebefore 0.3.6-150200.3.11.10.3.6-150200.3.11.1
SUSE:Linux Enterprise Module for Package Hub 15 SP6pipewirebefore 0.3.6-150200.3.11.10.3.6-150200.3.11.1
SUSE:Linux Enterprise Server 12 SP5-LTSSMozillaFirefoxbefore 140.0-112.270.2140.0-112.270.2

+1

Same product

mozilla: all records

Other 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 befKEV
    94Now
  • CVE-2019-11708Insufficient vetting of parameters passed with the Prompt:Open IPC message between child and parent processes can result in the non-sandboxeKEV
    87Now
  • 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 bypassKEV
    86Now

Published before and after this one in the same product

  • ← EarlierCVE-2025-6433Jun 24, 2025 · WebAuthn would allow a user to sign a challenge on a webpage with an invalid TLS certificate
    39Monitor
  • ← EarlierCVE-2025-6434Jun 24, 2025 · HTTPS-Only exception screen lacked anti-clickjacking delay
    17Monitor
  • Later →CVE-2025-6436Jun 24, 2025 · Memory safety bugs fixed in Firefox 140 and Thunderbird 140
    33Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
opensuse:firefox-esr140.1.0-1.1 · openSUSE:TumbleweedPackage registry (OSV)
opensuse:MozillaFirefox140.1.0-150200.152.193.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:MozillaFirefox-branding-SLE140-150200.9.21.1 · openSUSE:Leap 15.6Package registry (OSV)
opensuse:MozillaThunderbird140.1.0-150200.8.230.1 · openSUSE:Leap 15.6Package registry (OSV)
suse:MozillaFirefox140.0-112.270.2 · SUSE:Linux Enterprise Server 12 SP5-LTSSPackage registry (OSV)
suse:MozillaFirefox140.1.0-150200.152.193.1 · SUSE:Linux Enterprise Module for Desktop Applications 15 SP6Package registry (OSV)
suse:MozillaFirefox-branding-SLE140-150200.9.21.1 · SUSE:Linux Enterprise Module for Desktop Applications 15 SP6Package registry (OSV)
suse:MozillaFirefox-branding-SLE140-35.19.5 · SUSE:Linux Enterprise Server 12 SP5-LTSSPackage registry (OSV)
suse:MozillaThunderbird140.1.0-150200.8.230.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP6Package registry (OSV)
suse:pipewire0.3.6-150200.3.11.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP6Package registry (OSV)
suse:xdg-desktop-portal1.8.0-150200.5.8.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSPackage 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.

EPSS, last 120 days

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 researchers

Finders, 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-2024-3863434 days apartThe executable file warning was not presented when downloading .xrm-ms files.
    39Monitor

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.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-434 · Unrestricted Upload of File with Dangerous Type

CVSS vector

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

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.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records