Medium [CVE-2026-57019] Improper Validation of Specified Quantity in Input vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS)
This medium-severity Juniper Networks advisory covers CVE-2026-57019; related products: Junos OS, Junos, MX.
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Summary
An Improper Validation of Specified Quantity in Input vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).
When a specific packet is received from device in the same broadcast domain, an affected system calculates the packet size incorrectly. This causes further packet processing to fail, which triggers an FPC major error, resulting in a FPC reset impacting traffic until the FPC has automatically recovered.
Affected scenarios are: MAP-T, or non-IP traffic encapsulated in IP (e.g. MPLS over GRE).
When this issue happens the following logs can be observed:
fpc CMError: /fpc/0/pfe/0/cm/0/MQSS(0)/0/MQSS_CMERROR_LI_INT_REG_UNROLL_TAIL_LENGTH_OVF (0x2205eb), scope: pfe, category: functional, severity: major, module: MQSS(0), type: LI: Unroll TAIL length overflow, oc_category: default
fpc Performing action reset-fru for error /fpc/0/pfe/0/cm/0/MQSS(0)/0/MQSS_CMERROR_LI_INT_REG_UNROLL_TAIL_LENGTH_OVF (0x2205eb) in module: MQSS(0) with scope: pfe category: functional level: major, oc_category: default
This issue affects Junos OS on MX Series:
- all versions before 23.2R2-S6,
- 23.4 versions before 23.4R2-S7,
Affected products named by the advisory: MX.
Affected products named by the advisory: MX.
- * all versions before 23
Official advisory · high-confidence parse· fetched 3 months ago·verify at source
- 23.2R2-S6
- 23.4R2-S7
- 24.2R2-S4
- 24.4R2-S4
- 25.2R2
Official advisory · high-confidence parse· fetched 3 months ago·verify at source
Mitigation
Upgrade to a fixed release: 23.2R2-S6, 23.4R2-S7, 24.2R2-S4, 24.4R2-S4, 25.2R2. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 3 months ago·verify at source
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