What is CVE-2021-46837?A medium-severity flaw in Certified Asterisk, explained.
CVE-2021-46837 is a medium-severity flaw (CVSS 6.5) in Certified Asterisk from Asterisk, published on 30 August 2022. 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 4.4%. If you run an affected version, plan in the vendor’s fix.
Published 30 August 2022. Record last updated 28 January 2023. We keep this page's data up to date.
What is CVE-2021-46837? In plain terms.
It can be attacked from anywhere on the internet with an ordinary user account, and nobody has to click anything. If it works, the attacker can take it offline.
res_pjsip_t38 in Sangoma Asterisk 16.x before 16.16.2, 17.x before 17.9.3, and 18.x before 18.2.2, and Certified Asterisk before 16.8-cert7, allows an attacker to trigger a crash by sending an m=image line and zero port in a response to a T.38 re-invite initiated by Asterisk. This is a re-occurrence of the CVE-2019-15297 symptoms but not for exactly the same reason. The crash occurs because there is an append operation relative to the active topology, but this should instead be a replace operation.
What kind of flaw is it?
- CWE-476NULL Pointer Dereference
How an attack on it works
Read straight from its severity rating, translated out of the shorthand.
- Where an attacker can beAnywhere on the internet
- 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 take it offline
Severity vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Is CVE-2021-46837 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 4.4%. That can change at any time, which is why we keep watching.
Timeline
- Published
- Record last updated
CVE-2021-46837 scores 26. Action: Monitor.
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 isKey context
- Real threat activity around itKey context
85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score.
When CVE-2021-46837 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-2021-46837? 3 products.
The published record lists 3 products from 3 vendors. Versions are shown as published: "16.0.0 to before 16.16.2" means from 16.0.0 up to, but not including, 16.16.2. If you run one of these, check your version, then go to the fix below.
- Application
Certified Asterisk
by Asterisk
Affected versions16.8.016.8.0-cert116.8.0-cert216.8.0-cert316.8.0-cert416.8.0-cert516.8.0-cert6 - Application
Asterisk
by Digium
Affected versions16.0.0 to before 16.16.217.0.0 to before 17.9.318.0.0 to before 18.2.2 - Operating system
Debian Linux
by Debian
Affected versions9.010.011.0
How do I fix CVE-2021-46837? 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.
Does CVE-2021-46837 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.
Free plan, no card needed. Nothing to install.
1 new flaw affects software Acme tracks
res_pjsip_t38 in Sangoma Asterisk 16.x before 16.16.2, 17.x before 17.9.3, and 18.x before 18.2.2, and Certified Asterisk before 16.8-cert7, allows an attack...
- Matched to
- Certified Asterisk 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-2021-46837 is a medium-severity flaw in Certified Asterisk from Asterisk, published on 30 August 2022. It can be attacked from anywhere on the internet with an ordinary user account, and nobody has to click anything. If it works, the attacker can take it offline.
It scores 6.5 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2021-46837 is 26 out of 100, which is Low. Its action is "Monitor". 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 4.4%. That can change at any time, which is why we keep watching.
For Certified Asterisk from Asterisk: 16.8.0, 16.8.0-cert1, 16.8.0-cert2, 16.8.0-cert3, 16.8.0-cert4, 16.8.0-cert5 and 1 more. The record lists 3 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.