CVE-2026-21912
Junos OS: MX10k Series: 'show system firmware' CLI command may lead to LC480 or LC2101 line card reset
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the 'show system firmware' CLI command to cause an LC480 or LC2101 line card to reset.
On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the 'show system firmware' CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.This issue affects Junos OS on MX10k Series:
- all versions before 21.2R3-S10,
- from 21.4 before 21.4R3-S9,
- from 22.2 before 22.2R3-S7,
- from 22.4 before 22.4R3-S6,
- from 23.2 before 23.2R2-S2,
- from 23.4 before 23.4R2-S3,
- from 24.2 before 24.2R2.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Junos OS: MX10k Series: 'show system firmware' CLI command may lead to LC480 or LC2101 line card reset
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the 'show system firmware' CLI command to cause an LC480 or LC2101 line card to reset.
On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the 'show system firmware' CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.This issue affects Junos OS on MX10k Series:
- all versions before 21.2R3-S10,
- from 21.4 before 21.4R3-S9,
- from 22.2 before 22.2R3-S7,
- from 22.4 before 22.4R3-S6,
- from 23.2 before 23.2R2-S2,
- from 23.4 before 23.4R2-S3,
- from 24.2 before 24.2R2.
- Record
CVE-2026-21912- CVSS 4.0
- 6.8 Medium
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M/U:Amber - CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-367
- Updated
- 2026-11-02
EUVDEUVD-2026-2682
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the 'show system firmware' CLI command to cause an LC480 or LC2101 line card to reset.
On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the 'show system firmware' CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.This issue affects Junos OS on MX10k Series:
- all versions before 21.2R3-S10,
- from 21.4 before 21.4R3-S9,
- from 22.2 before 22.2R3-S7,
- from 22.4 before 22.4R3-S6,
- from 23.2 before 23.2R2-S2,
- from 23.4 before 23.4R2-S3,
- from 24.2 before 24.2R2.
- Record
EUVD-2026-2682- CVSS 4.0
- 6.8 Medium
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M/U:Amber - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-w5q5-7f2p-x4hm
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC...
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the 'show system firmware' CLI command to cause an LC480 or LC2101 line card to reset.
On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the 'show system firmware' CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.This issue affects Junos OS on MX10k Series:
- all versions before 21.2R3-S10,
- from 21.4 before 21.4R3-S9,
- from 22.2 before 22.2R3-S7,
- from 22.4 before 22.4R3-S6,
- from 23.2 before 23.2R2-S2,
- from 23.4 before 23.4R2-S3,
- from 24.2 before 24.2R2.
- Record
GHSA-w5q5-7f2p-x4hm- CVSS 4.0
- 6.8 Medium
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:X/RE:M/U:Amber - CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-367
- Updated
- 2026-11-02
NVD
A Time-of-check Time-of-use (TOCTOU) Race Condition vulnerability in the method to collect FPC Ethernet firmware statistics of Juniper Networks Junos OS on MX10k Series allows a local, low-privileged attacker executing the 'show system firmware' CLI command to cause an LC480 or LC2101 line card to reset.
On MX10k Series systems with LC480 or LC2101 line cards, repeated execution of the 'show system firmware' CLI command can cause the line card to crash and restart. Additionally, some time after the line card crashes, chassisd may also crash and restart, generating a core dump.This issue affects Junos OS on MX10k Series:
- all versions before 21.2R3-S10,
- from 21.4 before 21.4R3-S9,
- from 22.2 before 22.2R3-S7,
- from 22.4 before 22.4R3-S6,
- from 23.2 before 23.2R2-S2,
- from 23.4 before 23.4R2-S3,
- from 24.2 before 24.2R2.
- Record
CVE-2026-21912- CVSS 4.0
- 6.8 Medium
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:X/RE:M/U:Amber - CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - CVSS 3.1
- 4.7 Medium
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-367
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-21912 is a medium vulnerability (CVSS 6.8) in Juniper Junos, published January 15, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.11%, the 1st percentile. No source names a fixed version.