CVE-2024-0753Public exploitNetwork attack vector

HSTS bypass via incorrect ancestor policy lookup

Published Jan 23, 2024 · Updated Jun 7, 2025

HSTS enforcement in Firefox before 122, Firefox ESR before 115.7, and Thunderbird before 115.7 allows remote attackers to bypass HSTS. The HSTS lookup stops at the first ancestor with policy data and treats its missing includeSubDomains directive as overriding a higher ancestor's directive. Exploitation requires nested domains with conflicting policies and browser navigation to an HTTP descendant, permitting unencrypted access and exposure of non-Secure cookies.

CVSS severity6.5
Medium
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HSTS enforcement in Firefox before 122, Firefox ESR before 115.7, and Thunderbird before 115.7 allows remote attackers to bypass HSTS. The HSTS lookup stops at the first ancestor with policy data and treats its missing includeSubDomains directive as overriding a higher ancestor's directive. Exploitation requires nested domains with conflicting policies and browser navigation to an HTTP descendant, permitting unencrypted access and exposure of non-Secure cookies.

The record

CVE
CVE-2024-0753
Published
Jan 23, 2024
Updated
Jun 7, 2025
Vendor
Mozilla
Product
Firefox
Classifications
T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 23, 2024CVE publishedPublication date reported by the CVE source.
  2. Jun 7, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <122

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <122
Mozilla · Thunderbirdversion=unspecified <115.7
Mozilla · Firefox ESRversion=unspecified <115.7

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1557Adversary-in-the-Middle

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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