VulnerabilityPublished 12 Nov 2026Updated 13 Nov 2026

CVE-2026-126074: Rails · Active Storage makes it simple to upload and reference files in cloud services and attach

Affects railsSource GCVE Database

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Authoritative record:CVE-2026-126074· Medium 4.3

Not known to be exploited · CVSS 4.3 Medium · fixed in 8.1.4.1 : update rails when convenient.

Data as of 13 Nov 2026, 22:32 UTC

CVSS 3.1 base score

4.3Medium

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	4.3

Patch: Available – fixed in 8.1.4.1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: Low

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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to 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 13 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

Affected software

Product	Affected	Fixed in
Ubuntu 26.10rails`pkg:deb/ubuntu/rails?arch=source&distro=stonking`Other threats	Affected =2:7.2.3+dfsg-2 =2:7.2.3.2+dfsg-2	Fixed in–
Ubuntu 26.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=resolute`Other threats	Affected =2:7.2.2.1+dfsg-7 =2:7.2.2.2+dfsg-2 =2:7.2.3+dfsg-2	Fixed in–
Ubuntu 24.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=noble`Other threats	Affected =2:6.1.7.3+dfsg-2build1 =2:6.1.7.3+dfsg-3	Fixed in–
Ubuntu Pro 22.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=esm-apps/jammy`Other threats	Affected =2:6.0.3.7+dfsg-2 =2:6.1.4.1+dfsg-8ubuntu2 =2:6.1.4.1+dfsg-8ubuntu2+esm1	Fixed in–
Ubuntu Pro 20.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=esm-apps/focal`Other threats	Affected =2:5.2.2.1+dfsg-1ubuntu1 =2:5.2.3+dfsg-3 =2:5.2.3+dfsg-3ubuntu0.1~esm1	Fixed in–
Ubuntu Pro 18.04 LTSrails`pkg:deb/ubuntu/rails?arch=source&distro=esm-apps/bionic`Other threats	Affected 2:4.2.9-2 – 2:4.2.10-0ubuntu4+esm2 5 affected builds	Fixed in–

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

AI-suggested

Upgrade Rails Active Storage to version 8.1.4.1 or 8.0.5.2 or later, where this issue is fixed. No other mitigation is indicated or necessary. If upgrading is not immediately possible, consider purging or correcting filenames containing NUL bytes to prevent persistent errors.

Description

A vulnerability in Rails Active Storage prior to versions 8.1.4.1 and 8.0.5.2 allows a denial of service (DoS) condition when processing filenames containing NUL bytes. This occurs because Active Storage passes the stored filename unmodified to Ruby's File.basename and File.extname methods, which raise ArgumentError on NUL bytes. Databases like SQLite and MySQL/MariaDB that accept NUL bytes in string columns can persist such filenames, causing persistent errors on subsequent requests that handle the file, potentially leading to a DoS until the blob is purged or renamed. PostgreSQL is not affected as it rejects such rows.

Impact

This vulnerability can cause a persistent denial of service on pages that display affected blobs by raising exceptions on file operations involving filenames with embedded NUL bytes. It affects applications using databases that accept NUL bytes in string columns, such as SQLite and MySQL/MariaDB. There is no confidentiality or integrity impact reported. PostgreSQL users are not affected. The CVSS score is 4.3 (medium severity), reflecting a network attack vector with low complexity and no user interaction required, but limited impact to availability only.

Summary

Rails Active Storage versions before 8.1.4.1 and 8.0.5.2 do not sanitize client-supplied filenames containing NUL bytes. The methods ActiveStorage::Filename#base and #extension_with_delimiter pass these filenames directly to File.basename and File.extname, which raise exceptions on NUL bytes. When the database accepts these filenames (e.g., SQLite, MySQL/MariaDB), this leads to persistent errors on any operation that builds variants, previews, or renders the attachment, causing a denial of service condition. PostgreSQL databases are not affected due to rejection of such rows. The issue is fixed in Rails versions 8.1.4.1 and 8.0.5.2.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Nov 2026, 22:32 UTC

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