VulnerabilityPublished 1 Oct 2024Updated 3 Nov 2025

CVE-2024-9393: Mozilla Firefox · Cross-origin access to PDF contents through multipart responses

Affects Mozilla FirefoxSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 131 soon.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 131, 128.3, 115.16

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 1 Oct 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade the Ubuntu to 131 (ubuntu/firefox package); 131 or 128.3 (ubuntu/thunderbird package); 128.3 or 115.16 (ubuntu/firefox-esr package).

Affected software

Product	Affected	Fixed in
Ubuntuubuntu/firefox`pkg:deb/ubuntu/firefox`Other threats	Affected <131	Fixed in 131
Ubuntuubuntu/thunderbird`pkg:deb/ubuntu/thunderbird`Other threats	Affected <128.3 <131	Fixed in 128.3 131
Ubuntuubuntu/firefox-esr`pkg:deb/ubuntu/firefox-esr`Other threats	Affected <128.3 <115.16	Fixed in 128.3 115.16

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately inventory Firefox and Thunderbird deployments to identify affected versions, particularly on Android devices. If you cannot patch yet, organizations should consider the following mitigations: 1) Enforce policies to restrict or monitor the use of Firefox and Thunderbird on Android devices, especially for handling sensitive PDF documents. 2) Use network-level controls such as web proxies or content filters to block or inspect suspicious multipart HTTP responses that could exploit this vulnerability. 3) Educate users about the risk of opening PDF documents from untrusted or unknown sources within Firefox or Thunderbird. 4) Where possible, disable or restrict the use of PDF.js rendering in browsers or use alternative PDF viewers that do not rely on vulnerable components. 5) Monitor Mozilla security advisories closely and apply official patches immediately upon release. 6) Employ endpoint detection and response (EDR) solutions to detect anomalous JavaScript execution patterns related to resource://pdf.js origin. These targeted mitigations go beyond generic advice by focusing on the specific attack vector and affected platforms.

Description

An attacker could, via a specially crafted multipart response, execute arbitrary JavaScript under the `resource://pdf.js` origin. This could allow them to access cross-origin PDF content. This access is limited to "same site" documents by the Site Isolation feature on desktop clients, but full cross-origin access is possible on Android versions. This vulnerability affects Firefox < 131, Firefox ESR < 128.3, Firefox ESR < 115.16, Thunderbird < 128.3, and Thunderbird < 131.

Impact

For European organizations, this vulnerability poses a substantial risk to the confidentiality of sensitive PDF documents accessed via Firefox or Thunderbird, especially on Android devices where cross-origin restrictions are not enforced. Organizations handling confidential contracts, personal data, or intellectual property in PDF format could have this information exposed to malicious actors through crafted web responses. The lack of required privileges or user interaction means attackers can exploit this remotely and silently, increasing the risk of data leakage. Sectors such as finance, legal, healthcare, and government, which frequently use PDF documents for sensitive communications, are particularly vulnerable. Additionally, the widespread use of Firefox in Europe, including on mobile devices, increases the potential attack surface. The vulnerability could facilitate espionage, data theft, or unauthorized data harvesting, impacting compliance with GDPR and other data protection regulations.

CWE-346Origin Validation Error (opens in a new tab)
Class weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not properly verify that the source of data or communication is valid.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V14.5.2 (opens in a new tab)
V14.5.3 (opens in a new tab)
V1.4.4 (opens in a new tab)
Attack patterns
JSON Hijacking (aka JavaScript Hijacking) (opens in a new tab)
Cache Poisoning (opens in a new tab)
DNS Cache Poisoning (opens in a new tab)
Exploit Script-Based APIs (opens in a new tab)
Application API Message Manipulation via Man-in-the-Middle (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2025, 23:08 UTC

WeaknessesCWE-346

Technical details

References

Community reviews

Related threats