CVE-2026-126073
Action Pack: Possible cache poisoning in Action Pack content negotiation
Description
Action Pack is a framework for handling and responding to web requests. Prior to 8.1.4.1 and 8.0.5.2, Action Pack negotiates the format of a rendered response from the Accept, X-Requested-With and, for XHR requests without Accept, Content-Type request headers, but ActionController::Rendering#_set_vary_header adds Vary: Accept only when the request carries a usable Accept header and the response has no Vary header yet. A response to a request without Accept, or to an XHR request, therefore omits the headers that selected its representation, and a response whose Vary the application set before rendering (for example Vary: Accept-Language) never gains Accept. A shared cache that honours Vary could store such a response and serve it to later clients that request a different representation, possibly leading to cache poisoning in which visitors receive, until the entry expires, a page without its layout or HTML in place of JSON. The attacker cannot choose the content of the response. Applications that render negotiated responses from actions marked public (for example with expires_in ..., public: true) behind a shared cache that honours Vary, such as Thruster or Rack::Cache, are affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.
INFO
Published Date :
Nov. 10, 2026, 9:19 p.m.
Last Modified :
Nov. 12, 2026, 10:09 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Action Pack to version 8.1.4.1.
- Update Action Pack to version 8.0.5.2.
- Ensure Vary header is correctly set.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-126073.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-126073 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-126073
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-126073 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-126073 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Nov. 12, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-126073', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-11-12T16:26:31.033828Z'} -
New CVE Received by [email protected]
Nov. 10, 2026
Action Type Old Value New Value Added Description Action Pack is a framework for handling and responding to web requests. Prior to 8.1.4.1 and 8.0.5.2, Action Pack negotiates the format of a rendered response from the Accept, X-Requested-With and, for XHR requests without Accept, Content-Type request headers, but ActionController::Rendering#_set_vary_header adds Vary: Accept only when the request carries a usable Accept header and the response has no Vary header yet. A response to a request without Accept, or to an XHR request, therefore omits the headers that selected its representation, and a response whose Vary the application set before rendering (for example Vary: Accept-Language) never gains Accept. A shared cache that honours Vary could store such a response and serve it to later clients that request a different representation, possibly leading to cache poisoning in which visitors receive, until the entry expires, a page without its layout or HTML in place of JSON. The attacker cannot choose the content of the response. Applications that render negotiated responses from actions marked public (for example with expires_in ..., public: true) behind a shared cache that honours Vary, such as Thruster or Rack::Cache, are affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L Added CWE CWE-436 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/126xxx/CVE-2026-126073.json">CVE-2026-126073</a> Added Reference https://github.com/rails/rails/commit/7a955ca36779938267c93902c47d1f55bab99b4b Added Reference https://github.com/rails/rails/commit/b58c107abe9c1f10c1d6a4941402c60e4dc4742c Added Reference https://github.com/rails/rails/releases/tag/v8.0.5.2 Added Reference https://github.com/rails/rails/releases/tag/v8.1.4.1 Added Reference https://github.com/rails/rails/security/advisories/GHSA-r9jg-fmfx-2gv6