GHSA-r9jg-fmfx-2gv6

Suggest an improvement
Source
https://github.com/advisories/GHSA-r9jg-fmfx-2gv6
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/11/GHSA-r9jg-fmfx-2gv6/GHSA-r9jg-fmfx-2gv6.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-r9jg-fmfx-2gv6
Aliases
  • CVE-2026-126073
Published
2026-11-10T21:26:12Z
Modified
2026-11-10T21:45:03Z
Severity
  • 4.8 (Medium) CVSS_V3 - CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L CVSS Calculator
Summary
Action Pack: Possible cache poisoning in Action Pack content negotiation
Details

Impact

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.

Details

In the fixed releases, a rendered response whose format is not given by the URL lists Accept and X-Requested-With in Vary, and also Content-Type for an XHR request without Accept; when config.action_dispatch.ignore_accept_header is enabled, it lists only X-Requested-With. These fields are appended to an existing Vary value rather than skipped, and Vary: * is left unchanged. Shared caches can store more variants of such responses than before. See the Action Pack CHANGELOG for details.

Workarounds

Set Vary: Accept, X-Requested-With on negotiated responses in the application, for example in an after_action, or do not mark negotiated responses public.

Releases

The fixed releases are available at the normal locations.

Patches for those who cannot upgrade at once:

Credit

This issue was found by the Anthropic OSS Scanner (ANT-2026-7GHGLQGO, ANT-2026-5MT6C2R3).

Database specific 
{
    "cwe_ids": [
        "CWE-436"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-11-10T21:26:12Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
}
References

Affected packages

RubyGems / actionpack

Package

Name
actionpack
Purl
pkg:gem/actionpack

Affected ranges

Type
ECOSYSTEM
Events
Introduced
8.1
Fixed
8.1.4.1

Affected versions

8.*
8.1.0
8.1.1
8.1.2
8.1.2.1
8.1.3
8.1.3.1
8.1.4

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/11/GHSA-r9jg-fmfx-2gv6/GHSA-r9jg-fmfx-2gv6.json"

RubyGems / actionpack

Package

Name
actionpack
Purl
pkg:gem/actionpack

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
8.0.5.2

Affected versions

0.*
0.9.0
0.9.5
1.*
1.0.0
1.0.1
1.1.0
1.2.0
1.3.0
1.3.1
1.4.0
1.5.0
1.5.1
1.6.0
1.7.0
1.8.0
1.8.1
1.9.0
1.9.1
1.10.1
1.10.2
1.11.0
1.11.1
1.11.2
1.12.0
1.12.1
1.12.2
1.12.3
1.12.4
1.12.5
1.13.0
1.13.1
1.13.2
1.13.3
1.13.4
1.13.5
1.13.6
2.*
2.0.0
2.0.1
2.0.2
2.0.4
2.0.5
2.1.0
2.1.1
2.1.2
2.2.2
2.2.3
2.3.2
2.3.3
2.3.4
2.3.5
2.3.6
2.3.7
2.3.8.pre1
2.3.8
2.3.9.pre
2.3.9
2.3.10
2.3.11
2.3.12
2.3.14
2.3.15
2.3.16
2.3.17
2.3.18
3.*
3.0.0.beta
3.0.0.beta2
3.0.0.beta3
3.0.0.beta4
3.0.0.rc
3.0.0.rc2
3.0.0
3.0.1
3.0.2
3.0.3
3.0.4.rc1
3.0.4
3.0.5.rc1
3.0.5
3.0.6.rc1
3.0.6.rc2
3.0.6
3.0.7.rc1
3.0.7.rc2
3.0.7
3.0.8.rc1
3.0.8.rc2
3.0.8.rc4
3.0.8
3.0.9.rc1
3.0.9.rc3
3.0.9.rc4
3.0.9.rc5
3.0.9
3.0.10.rc1
3.0.10
3.0.11
3.0.12.rc1
3.0.12
3.0.13.rc1
3.0.13
3.0.14
3.0.15
3.0.16
3.0.17
3.0.18
3.0.19
3.0.20
3.1.0.beta1
3.1.0.rc1
3.1.0.rc2
3.1.0.rc3
3.1.0.rc4
3.1.0.rc5
3.1.0.rc6
3.1.0.rc8
3.1.0
3.1.1.rc1
3.1.1.rc2
3.1.1.rc3
3.1.1
3.1.2.rc1
3.1.2.rc2
3.1.2
3.1.3
3.1.4.rc1
3.1.4
3.1.5.rc1
3.1.5
3.1.6
3.1.7
3.1.8
3.1.9
3.1.10
3.1.11
3.1.12
3.2.0.rc1
3.2.0.rc2
3.2.0
3.2.1
3.2.2.rc1
3.2.2
3.2.3.rc1
3.2.3.rc2
3.2.3
3.2.4.rc1
3.2.4
3.2.5
3.2.6
3.2.7.rc1
3.2.7
3.2.8.rc1
3.2.8.rc2
3.2.8
3.2.9.rc1
3.2.9.rc2
3.2.9.rc3
3.2.9
3.2.10
3.2.11
3.2.12
3.2.13.rc1
3.2.13.rc2
3.2.13
3.2.14.rc1
3.2.14.rc2
3.2.14
3.2.15.rc1
3.2.15.rc2
3.2.15.rc3
3.2.15
3.2.16
3.2.17
3.2.18
3.2.19
3.2.20
3.2.21
3.2.22
3.2.22.1
3.2.22.2
3.2.22.3
3.2.22.4
3.2.22.5
4.*
4.0.0.beta1
4.0.0.rc1
4.0.0.rc2
4.0.0
4.0.1.rc1
4.0.1.rc2
4.0.1.rc3
4.0.1.rc4
4.0.1
4.0.2
4.0.3
4.0.4.rc1
4.0.4
4.0.5
4.0.6.rc1
4.0.6.rc2
4.0.6.rc3
4.0.6
4.0.7
4.0.8
4.0.9
4.0.10.rc1
4.0.10.rc2
4.0.10
4.0.11
4.0.11.1
4.0.12
4.0.13.rc1
4.0.13
4.1.0.beta1
4.1.0.beta2
4.1.0.rc1
4.1.0.rc2
4.1.0
4.1.1
4.1.2.rc1
4.1.2.rc2
4.1.2.rc3
4.1.2
4.1.3
4.1.4
4.1.5
4.1.6.rc1
4.1.6.rc2
4.1.6
4.1.7
4.1.7.1
4.1.8
4.1.9.rc1
4.1.9
4.1.10.rc1
4.1.10.rc2
4.1.10.rc3
4.1.10.rc4
4.1.10
4.1.11
4.1.12.rc1
4.1.12
4.1.13.rc1
4.1.13
4.1.14.rc1
4.1.14.rc2
4.1.14
4.1.14.1
4.1.14.2
4.1.15.rc1
4.1.15
4.1.16.rc1
4.1.16
4.2.0.beta1
4.2.0.beta2
4.2.0.beta3
4.2.0.beta4
4.2.0.rc1
4.2.0.rc2
4.2.0.rc3
4.2.0
4.2.1.rc1
4.2.1.rc2
4.2.1.rc3
4.2.1.rc4
4.2.1
4.2.2
4.2.3.rc1
4.2.3
4.2.4.rc1
4.2.4
4.2.5.rc1
4.2.5.rc2
4.2.5
4.2.5.1
4.2.5.2
4.2.6.rc1
4.2.6
4.2.7.rc1
4.2.7
4.2.7.1
4.2.8.rc1
4.2.8
4.2.9.rc1
4.2.9.rc2
4.2.9
4.2.10.rc1
4.2.10
4.2.11
4.2.11.1
4.2.11.2
4.2.11.3
5.*
5.0.0.beta1
5.0.0.beta1.1
5.0.0.beta2
5.0.0.beta3
5.0.0.beta4
5.0.0.racecar1
5.0.0.rc1
5.0.0.rc2
5.0.0
5.0.0.1
5.0.1.rc1
5.0.1.rc2
5.0.1
5.0.2.rc1
5.0.2
5.0.3
5.0.4.rc1
5.0.4
5.0.5.rc1
5.0.5.rc2
5.0.5
5.0.6.rc1
5.0.6
5.0.7
5.0.7.1
5.0.7.2
5.1.0.beta1
5.1.0.rc1
5.1.0.rc2
5.1.0
5.1.1
5.1.2.rc1
5.1.2
5.1.3.rc1
5.1.3.rc2
5.1.3.rc3
5.1.3
5.1.4.rc1
5.1.4
5.1.5.rc1
5.1.5
5.1.6
5.1.6.1
5.1.6.2
5.1.7.rc1
5.1.7
5.2.0.beta1
5.2.0.beta2
5.2.0.rc1
5.2.0.rc2
5.2.0
5.2.1.rc1
5.2.1
5.2.1.1
5.2.2.rc1
5.2.2
5.2.2.1
5.2.3.rc1
5.2.3
5.2.4.rc1
5.2.4
5.2.4.1
5.2.4.2
5.2.4.3
5.2.4.4
5.2.4.5
5.2.4.6
5.2.5
5.2.6
5.2.6.1
5.2.6.2
5.2.6.3
5.2.7
5.2.7.1
5.2.8
5.2.8.1
6.*
6.0.0.beta1
6.0.0.beta2
6.0.0.beta3
6.0.0.rc1
6.0.0.rc2
6.0.0
6.0.1.rc1
6.0.1
6.0.2.rc1
6.0.2.rc2
6.0.2
6.0.2.1
6.0.2.2
6.0.3.rc1
6.0.3
6.0.3.1
6.0.3.2
6.0.3.3
6.0.3.4
6.0.3.5
6.0.3.6
6.0.3.7
6.0.4
6.0.4.1
6.0.4.2
6.0.4.3
6.0.4.4
6.0.4.5
6.0.4.6
6.0.4.7
6.0.4.8
6.0.5
6.0.5.1
6.0.6
6.0.6.1
6.1.0.rc1
6.1.0.rc2
6.1.0
6.1.1
6.1.2
6.1.2.1
6.1.3
6.1.3.1
6.1.3.2
6.1.4
6.1.4.1
6.1.4.2
6.1.4.3
6.1.4.4
6.1.4.5
6.1.4.6
6.1.4.7
6.1.5
6.1.5.1
6.1.6
6.1.6.1
6.1.7
6.1.7.1
6.1.7.2
6.1.7.3
6.1.7.4
6.1.7.5
6.1.7.6
6.1.7.7
6.1.7.8
6.1.7.9
6.1.7.10
7.*
7.0.0.alpha1
7.0.0.alpha2
7.0.0.rc1
7.0.0.rc2
7.0.0.rc3
7.0.0
7.0.1
7.0.2
7.0.2.1
7.0.2.2
7.0.2.3
7.0.2.4
7.0.3
7.0.3.1
7.0.4
7.0.4.1
7.0.4.2
7.0.4.3
7.0.5
7.0.5.1
7.0.6
7.0.7
7.0.7.1
7.0.7.2
7.0.8
7.0.8.1
7.0.8.2
7.0.8.3
7.0.8.4
7.0.8.5
7.0.8.6
7.0.8.7
7.0.10
7.1.0.beta1
7.1.0.rc1
7.1.0.rc2
7.1.0
7.1.1
7.1.2
7.1.3
7.1.3.1
7.1.3.2
7.1.3.3
7.1.3.4
7.1.4
7.1.4.1
7.1.4.2
7.1.5
7.1.5.1
7.1.5.2
7.1.6
7.2.0.beta1
7.2.0.beta2
7.2.0.beta3
7.2.0.rc1
7.2.0
7.2.1
7.2.1.1
7.2.1.2
7.2.2
7.2.2.1
7.2.2.2
7.2.3
7.2.3.1
7.2.3.2
7.2.4
8.*
8.0.0.beta1
8.0.0.rc1
8.0.0.rc2
8.0.0
8.0.0.1
8.0.1
8.0.2
8.0.2.1
8.0.3
8.0.4
8.0.4.1
8.0.5
8.0.5.1

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/11/GHSA-r9jg-fmfx-2gv6/GHSA-r9jg-fmfx-2gv6.json"