CVE-2024-0743VulnerabilityPublished 23 Jan 2024Updated 3 Nov 2025

CVE-2024-0743: Mozilla Firefox · Crash in NSS TLS method

Affects Mozilla FirefoxSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 122 or 115.9 soon.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 1.2% chance of exploitation in 30 days – higher than 69% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 122, 115.9

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

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Jan 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 2026-10-25.

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 Mozilla Firefox to 122 or 115.9.

Affected software

Product	Affected	Fixed in
Mozilla Firefox	Affected <122 <115.9	Fixed in 122 115.9

AI-suggested

European organizations should immediately verify the versions of Mozilla Firefox and Thunderbird deployed across their environments and prioritize upgrading to Firefox 122 or later, and Thunderbird 115.9 or later, where the vulnerability is patched. Network-level protections such as intrusion detection/prevention systems (IDS/IPS) should be tuned to detect anomalous TLS handshake patterns that could indicate exploitation attempts. Organizations should also consider implementing application-layer firewalls or TLS inspection proxies to monitor and block suspicious TLS traffic. Regular vulnerability scanning and asset inventory management will help identify unpatched systems. For environments where immediate patching is not feasible, temporary mitigations include restricting access to Firefox and Thunderbird from untrusted networks or using endpoint protection solutions to monitor for crashes and unusual application behavior. User awareness campaigns should emphasize the importance of applying software updates promptly. Finally, organizations should test patches in controlled environments to ensure compatibility and stability before wide deployment.

Description

An unchecked return value in TLS handshake code could have caused a potentially exploitable crash. This vulnerability affects Firefox < 122, Firefox ESR < 115.9, and Thunderbird < 115.9.

Impact

For European organizations, this vulnerability poses a significant risk to the availability of critical communication tools such as Firefox and Thunderbird, which are widely used for web browsing and email. A successful exploitation could lead to denial of service conditions, disrupting business operations, communications, and access to web-based services. Sectors such as finance, government, healthcare, and critical infrastructure that rely on secure and reliable communications could face operational interruptions. While confidentiality and integrity are not directly compromised, the availability impact can indirectly affect business continuity and incident response capabilities. Additionally, denial of service attacks exploiting this vulnerability could be used as part of larger multi-vector attacks or to create distractions for other malicious activities. The lack of required authentication and user interaction lowers the barrier for attackers, increasing the risk profile. Organizations with remote workforces relying on Firefox and Thunderbird are particularly vulnerable to disruptions. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, emphasizing the need for proactive patch management.

CWE-252Unchecked Return Value (opens in a new tab)
Base weaknessLikelihood of exploit: LowOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions.
Implementation
Check the results of all functions that return a value and verify that the value is expected.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Implementation
Ensure that you account for all possible return values from the function.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 3 Nov 2025, 23:11 UTC

WeaknessesCWE-252

Technical details

References

Community reviews

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