VulnerabilityPublished 23 Jan 2024Updated 7 Jun 2025

CVE-2024-0753: Mozilla Firefox · HSTS policy on subdomain could bypass policy of upper domain

Affects Mozilla FirefoxSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 122 or 115.7 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.7% chance of exploitation in 30 days – higher than 53% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 122, 115.7

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: None
Integrity: High
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: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 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 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 or the CVSS exploit maturity 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 115.7.

Affected software

Product	Affected	Fixed in
Mozilla Firefox	Affected <122 <115.7	Fixed in 122 115.7

AI-suggested

European organizations should prioritize updating all instances of Mozilla Firefox to version 122 or later, and Thunderbird to version 115.7 or later, to ensure the vulnerability is patched. Beyond patching, organizations should audit their HSTS configurations, especially for subdomains, to ensure policies are correctly inherited and enforced. Implementing HSTS preload lists for critical domains can provide an additional layer of protection by hardcoding HSTS policies into browsers. Network-level protections such as DNS security extensions (DNSSEC) and monitoring for DNS spoofing or subdomain takeovers can reduce the risk of attackers controlling subdomains. User awareness training should emphasize caution when interacting with unfamiliar subdomains or links, as user interaction is required for exploitation. Additionally, organizations could consider deploying endpoint security solutions that monitor for anomalous TLS downgrade attempts or MITM indicators. For sensitive environments, using browser security policies or enterprise configurations to restrict browser versions and enforce strict HTTPS usage can further mitigate risks.

Description

In specific HSTS configurations an attacker could have bypassed HSTS on a subdomain. This vulnerability affects Firefox < 122, Firefox ESR < 115.7, and Thunderbird < 115.7.

Impact

For European organizations, this vulnerability poses a moderate risk primarily to the integrity of web communications when using affected versions of Firefox or Thunderbird. Organizations relying on these browsers for accessing internal or external web services that implement HSTS policies could be exposed to man-in-the-middle attacks if an attacker controls or can spoof a subdomain. This could lead to interception or manipulation of sensitive data, including credentials, confidential communications, or session tokens. The risk is heightened in environments where users frequently access subdomains that may not be fully controlled or audited by the organization. While the vulnerability does not directly impact confidentiality or availability, the potential for integrity compromise can undermine trust in secure communications and lead to further exploitation. Given the widespread use of Firefox and Thunderbird in Europe, especially in government, finance, and critical infrastructure sectors, the vulnerability could affect a broad range of users. However, the requirement for user interaction and the absence of known active exploits reduce the immediate threat level. Nonetheless, targeted attacks against high-value European entities could leverage this flaw to bypass HSTS protections.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 8 Jul 2025, 19:42 UTC

Technical details

References

Community reviews

Related threats