Firefox: Sensitive Cookie with Improper SameSite Attribute
CVE-2024-6611 is a critical-severity sensitive cookie with improper samesite attribute vulnerability in Firefox from Mozilla, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 128 as the first without the flaw, so updating Firefox to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update Firefox to 128 or a later version.
- Update Thunderbird to 128 or a later version.
- Read the advisory on mozilla.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Mozilla | Firefox | before 128 | 128 |
| Mozilla | Thunderbird | before 128 | 128 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).
Official description
A nested iframe, triggering a cross-site navigation, could send SameSite=Strict or Lax cookies. This vulnerability affects Firefox < 128 and Thunderbird < 128.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Sensitive Cookie with Improper SameSite Attribute
The SameSite attribute for sensitive cookies is not set, or an insecure value is used.
How developers prevent this class of flaw
- Set the SameSite attribute of a sensitive cookie to Lax or Strict. This instructs the browser to apply this cookie only to same-domain requests, which provides a good Defense in Depth against CSRF attacks. When the Lax value is in use, cookies are also sent for top-level cross-domain navigation via HTTP GET, HEAD, OPTIONS, and TRACE methods, but not for other HTTP methods that are more likely to cause side-effects of state mutation.
More Sensitive Cookie with Improper SameSite Attribute vulnerabilities (CWE-1275)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
- bugzilla.mozilla.org/show_bug.cgi?id=1844827Issue Tracking
Other vulnerabilities in Firefox
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- 8.8 High severity
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