What is CVE-2021-41091?A medium-severity flaw in Moby, explained.
CVE-2021-41091 is a medium-severity flaw (CVSS 6.3) in Moby from Mobyproject, published on 4 October 2021. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 2.8%. If you run an affected version, plan in the vendor’s fix.
Published 4 October 2021. Record last updated 7 November 2023. We keep this page's data up to date.
What is CVE-2021-41091? In plain terms.
An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read some data, change some data and slow it down.
Moby is an open-source project created by Docker to enable software containerization. A bug was found in Moby (Docker Engine) where the data directory (typically `/var/lib/docker`) contained subdirectories with insufficiently restricted permissions, allowing otherwise unprivileged Linux users to traverse directory contents and execute programs. When containers included executable programs with extended permission bits (such as `setuid`), unprivileged Linux users could discover and execute those programs. When the UID of an unprivileged Linux user on the host collided with the file owner or group inside a container, the unprivileged Linux user on the host could discover, read, and modify those files. This bug has been fixed in Moby (Docker Engine) 20.10.9. Users should update to this version as soon as possible. Running containers should be stopped and restarted for the permissions to be fixed. For users unable to upgrade limit access to the host to trusted users. Limit access to host volumes to trusted containers.
What kind of flaw is it?
- CWE-281Improper Preservation of Permissions
- CWE-732Incorrect Permission Assignment for Critical Resource
How an attack on it works
Read straight from its severity rating, translated out of the shorthand.
- Where an attacker can beAlready on the device
- How hard it is to pull offEasy: no special conditions
- Login needed firstAn ordinary user account
- Does someone have to clickNo, nobody has to do anything
- What an attacker getsCan read some data, change some data and slow it down
Severity vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
Is CVE-2021-41091 being exploited? Not that we know of.
It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 2.8%. That can change at any time, which is why we keep watching.
Timeline
- Published
- Record last updated
CVE-2021-41091 scores 44. Action: Plan remediation.
We keep the score of every published flaw up to date as the evidence changes. Four things go into the score, and evidence that criminals are actually using it counts most. In order:
- Evidence it is being exploitedBiggest factor
- How severe it isStrong factor
- How widely exposed it isSmaller factor
- Threat activity around itSmaller factor
85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score.
When CVE-2021-41091 matches software you track, it lands in your list with its score and the reasons behind it.
See your own ranked list →Who is affected by CVE-2021-41091? 2 products.
The published record lists 2 products from 2 vendors. Versions are shown as published: "before 20.10.9" means every version up to, but not including, 20.10.9. If you run one of these, check your version, then go to the fix below.
- Application
Moby
by Mobyproject
Affected versionsbefore 20.10.9 - Operating system
Fedora
Affected versions3435
How do I fix CVE-2021-41091? Four steps.
- Check whether you run itCompare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
- Apply the vendor’s fixInstall the update named in the vendor’s advisory. We’ve put the advisory first in the list.
- If you can’t patch todayFollow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
- Keep an eye on itTrack the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.
References
5 linksDoes CVE-2021-41091 affect you? We'll keep checking.
Looking flaws up one at a time doesn't scale. Tell us what you run once, and we tell you which flaws matter to you, in what order, and keep watching for new ones.
- Tell us what you runPick your software from a list, or let us work it out from your website.
- We match it to every flawOver 400,000 published flaws, checked against your list.
- Ranked by real-world riskA 0 to 100 score, led by evidence criminals are using it.
- Told as soon as we knowAn alert by email, in the app or by webhook to your own tools.
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1 new flaw affects software Acme tracks
Moby is an open-source project created by Docker to enable software containerization. A bug was found in Moby (Docker Engine) where the data directory (typic...
- Matched to
- Moby on Acme's software list
- What to do
- Plan in the vendor’s update
Sent to the alert recipients Acme chose. Also in the app and to Acme's webhook.
CVE-2021-41091 is a medium-severity flaw in Moby from Mobyproject, published on 4 October 2021. An attacker has to be already on the device with an ordinary user account, and nobody has to click anything. If it works, the attacker can read some data, change some data and slow it down.
It scores 6.3 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2021-41091 is 44 out of 100, which is Medium. Its action is "Plan remediation". No sign of exploitation and a low forecast. Patch it in your normal update cycle.
It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 2.8%. That can change at any time, which is why we keep watching.
For Moby from Mobyproject: before 20.10.9. The record lists 2 products in all, each with its versions, under "Who is affected" on this page.
Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.