What is CVE-2021-0295?A medium-severity flaw in Junos, explained.
CVE-2021-0295 is a medium-severity flaw (CVSS 6.1) in Junos from Juniper, published on 15 July 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 1.1%. If you run an affected version, plan in the vendor’s fix.
Published 15 July 2021. Record last updated 28 July 2021. We keep this page's data up to date.
What is CVE-2021-0295? In plain terms.
An attacker has to be on the same local network without logging in, and nobody has to click anything. If it works, the attacker can change some data and slow it down.
A vulnerability in the Distance Vector Multicast Routing Protocol (DVMRP) of Juniper Networks Junos OS on the QFX10K Series switches allows an attacker to trigger a packet forwarding loop, leading to a partial Denial of Service (DoS). The issue is caused by DVMRP packets looping on a multi-homed Ethernet Segment Identifier (ESI) when VXLAN is configured. DVMRP packets received on a multi-homed ESI are sent to the peer, and then incorrectly forwarded out the same ESI, violating the split horizon rule. This issue only affects QFX10K Series switches, including the QFX10002, QFX10008, and QFX10016. Other products and platforms are unaffected by this vulnerability. This issue affects Juniper Networks Junos OS on QFX10K Series: 17.3 versions prior to 17.3R3-S12; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 version 18.2R1 and later versions; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R2-S9, 18.4R3-S8; 19.1 versions prior to 19.1R3-S5; 19.2 versions prior to 19.2R1-S7, 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3; 20.2 versions prior to 20.2R3; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R2.
What kind of flaw is it?
- CWE-697Incorrect Comparison
How an attack on it works
Read straight from its severity rating, translated out of the shorthand.
- Where an attacker can beOn the same local network
- How hard it is to pull offEasy: no special conditions
- Login needed firstNo login needed
- Does someone have to clickNo, nobody has to do anything
- What an attacker getsCan change some data and slow it down
Severity vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L
Is CVE-2021-0295 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 1.1%. That can change at any time, which is why we keep watching.
Timeline
- Published
- Record last updated
CVE-2021-0295 scores 20. 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 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-2021-0295 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-2021-0295? 5 products.
The published record lists 5 products from 1 vendor. If you run one of these, check your version, then go to the fix below.
- Operating system
Junos
by Juniper
Affected versions17.317.3-r117.3-r1-s117.3-r1-s417.3-r217.3-r2-s117.3-r2-s217.3-r2-s317.3-r2-s417.3-r2-s517.3-r317.3-r3-s117.3-r3-s217.3-r3-s3 - Hardware
Qfx10000
by Juniper
Affected versionsversion not specified - Hardware
Qfx10002
by Juniper
Affected versionsversion not specified - Hardware
Qfx10008
by Juniper
Affected versionsversion not specified - Hardware
Qfx10016
by Juniper
Affected versionsversion not specified
How do I fix CVE-2021-0295? 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
1 linkDoes CVE-2021-0295 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.
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1 new flaw affects software Acme tracks
A vulnerability in the Distance Vector Multicast Routing Protocol (DVMRP) of Juniper Networks Junos OS on the QFX10K Series switches allows an attacker to tr...
- Matched to
- Junos 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-2021-0295 is a medium-severity flaw in Junos from Juniper, published on 15 July 2021. An attacker has to be on the same local network without logging in, and nobody has to click anything. If it works, the attacker can change some data and slow it down.
It scores 6.1 out of 10 on the CVSS severity scale, which is medium. Our risk score for CVE-2021-0295 is 20 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 1.1%. That can change at any time, which is why we keep watching.
For Junos from Juniper: 17.3, 17.3-r1, 17.3-r1-s1, 17.3-r1-s4, 17.3-r2, 17.3-r2-s1 and 193 more. The record lists 5 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.