CVE-2017-10621Junos OS: Denial of service vulnerability in telnetd
- 5.3MediumCVSS base score
- 1.8%Exploitation in 30 daysEPSS · top 21% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
A denial of service vulnerability in telnetd service on Juniper Networks Junos OS allows remote unauthenticated attackers to cause a denial of service. Affected Junos OS releases are: 12.1X46 prior to 12.1X46-D71; 12.3X48 prior to 12.3X48-D50; 14.1 prior to 14.1R8-S5, 14.1R9; 14.1X53 prior to 14.1X53-D50; 14.2 prior to 14.2R7-S9, 14.2R8; 15.1 prior to 15.1F2-S16, 15.1F5-S7, 15.1F6-S6, 15.1R5-S2, 15.1R6; 15.1X49 prior to 15.1X49-D90; 15.1X53 prior to 15.1X53-D47; 16.1 prior to 16.1R4-S1, 16.1R5; 16.2 prior to 16.2R1-S3, 16.2R2;
Timeline
ID reserved
By juniper
- 4 months later
· 4 months later
Published
- 7 years later
· 7 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| juniperCNA (assigner) | 3.0 | Medium5.3 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
| NVDNVD · Modified | 3.0 | Medium5.3 | CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
- EPSS (exploitation in 30 days)
- 1.8% · top 21% of all CVEs (12 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.
Affected products
- affected 12.1X46 prior to 12.1X46-D71
- affected 12.3X48 prior to 12.3X48-D50
- affected 14.1 prior to 14.1R8-S5, 14.1R9
- affected 14.1X53 prior to 14.1X53-D50
- affected 14.2 prior to 14.2R7-S9, 14.2R8
- affected 15.1 prior to 15.1F2-S16, 15.1F5-S7, 15.1F6-S6, 15.1R5-S2, 15.1R6
- affected 15.1X49 prior to 15.1X49-D90
- affected 15.1X53 prior to 15.1X53-D47
- affected 16.1 prior to 16.1R4-S1, 16.1R5
- affected 16.2 prior to 16.2R1-S3, 16.2R2
What to do
Workaround: Disabling the telnet service would completely mitigate this issue. Reducing the maximum number of connections to a value between 1 and 250 would help mitigate this vulnerability. For example: user@junos# set system services telnet connection-limit 100
Workaround: It is good security practice to limit the exploitable attack surface of critical infrastructure networking equipment. Use access lists or firewall filters to limit access to the device from trusted, administrative networks or hosts.
References
References1
- https://kb.juniper.net/JSA10817 (opens in a new tab)x_refsource_CONFIRMx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2017-2268 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2017-10621)Record last updated .