VulnerabilityPublished 12 Nov 2026

CVE-2026-126081: Action Pack · Possible Strong Parameters Bypass in Parameters#each_key

Affects actionpackSource GCVE Database

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Mentioned vulnerabilities

CVE-2020-8164

Authoritative record:CVE-2026-126081· High 7.5

Not known to be exploited · CVSS 7.5 High : upgrade to 8.1.4.1 soon.

Data as of 13 Nov 2026, 00:08 UTC

CVSS 3.1 base score

7.5High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	7.5

Patch: Available – fixed in 8.1.4.1, 8.0.5.2

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
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: None: The vulnerable system can be exploited without any interaction from any user.
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 10 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 12 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 actionpack to 8.1.4.1; actionpack to 8.0.5.2.

Affected software

Product	Affected	Fixed in
RubyGemsactionpack	Affected >=8.1.0.beta1 <8.1.4.1	Fixed in 8.1.4.1
RubyGemsactionpack	Affected <8.0.5.2	Fixed in 8.0.5.2

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available in actionpack versions 8.0.5.2 and 8.1.4.1 that fixes the behavior of Parameters#each_key. Applications should upgrade to these versions or later. For those unable to upgrade immediately, patches are available for backporting. As a workaround, avoid using the return value of each_key; instead, call it only for its block and pass the permitted Parameters instance to mass assignment methods. Rails itself does not call each_key in a vulnerable manner, so this issue primarily affects applications with custom code using each_key's return value.

Description

A vulnerability in Action Pack's Parameters#each_key method allows a possible strong parameters bypass. When called with a block, each_key returns an internal hash that does not respond to permitted?, enabling mass assignment to accept unpermitted parameters. This can allow a remote unauthenticated attacker to set unauthorized attributes, such as authorization flags. The issue affects versions prior to 8.0.5.2 and between 8.1.0.beta1 and 8.1.4.1. Fixed versions 8.0.5.2 and 8.1.4.1 correct the behavior to return the Parameters instance, which enforces permission checks.

Impact

The vulnerability allows remote unauthenticated attackers to bypass strong parameter protections by passing the return value of each_key to mass assignment methods, potentially setting unauthorized attributes such as authorization flags. This can lead to privilege escalation or unauthorized data modification. The CVSS 3.0 score is 7.5 (High), reflecting network attack vector, low complexity, no privileges required, no user interaction, unchanged scope, no confidentiality impact, high integrity impact, and no availability impact.

CWE-915Improperly Controlled Modification of Dynamically-Determined Object Attributes (opens in a new tab)
Base weaknessOWASP Top 10 A08:2025: Software or Data Integrity Failures (opens in a new tab)
The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.
Implementation
If available, use features of the language or framework that allow specification of allowlists of attributes or fields that are allowed to be modified. If possible, prefer allowlists over denylists.
Architecture and Design · Implementation
If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
Implementation · Input Validation
For any externally-influenced input, check the input against an allowlist of internal object attributes or fields that are allowed to be modified.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
Software Supply Chain Security (opens in a new tab)
Infrastructure as Code (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Nov 2026, 00:08 UTC

WeaknessesCWE-915

Technical details

References

Community reviews

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