CVE-2026-33800 (GCVE-0-2026-33800)

Vulnerability from cvelistv5 – Published: 2026-07-09 21:03 – Updated: 2026-07-09 21:03
VLAI
Title
Junos OS: MX Series: In a VC scenario a high rate of micro-BFD session flaps will cause an FPC crash
Summary
An Unchecked Input for Loop Condition 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).Micro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a Virtual-Chassis (VC) scenario with locality‑bias configured, processing takes a significant amount of time for each event. If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage. This issue only affects MX series FPCs up to and including MPC9. It does not affect MPC10/11, LC4800/9600 and MX304. This issue affects Junos OS on MX Series: * all versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S8, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2-S3, * 25.2 versions before 25.2R2.
Severity
6.5 (Medium)
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.1 (High)
CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M
CWE
  • CWE-606 - Unchecked Input for Loop Condition
Assigner
References
Impacted products
Vendor Product Version
Juniper Networks Junos OS Affected: 0 , < 23.2R2-S7 (custom)
Affected: 23.4 , < 23.4R2-S8 (custom)
Affected: 24.2 , < 24.2R2-S4 (custom)
Affected: 24.4 , < 24.4R2-S3 (custom)
Affected: 25.2 , < 25.2R2 (custom)
Create a notification for this product.
Date Public
2026-07-08 16:00
Show details on NVD website
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "platforms": [
            "MX Series"
          ],
          "product": "Junos OS",
          "vendor": "Juniper Networks",
          "versions": [
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              "lessThan": "23.2R2-S7",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
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            {
              "lessThan": "23.4R2-S8",
              "status": "affected",
              "version": "23.4",
              "versionType": "custom"
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            {
              "lessThan": "24.2R2-S4",
              "status": "affected",
              "version": "24.2",
              "versionType": "custom"
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            {
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              "status": "affected",
              "version": "24.4",
              "versionType": "custom"
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              "version": "25.2",
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              "value": "To be exposed to this issue an MX VC needs to be configured with locality bias as follows:\u003cbr\u003e\u003cbr\u003e\u003ctt\u003e[ virtual-chassis locality-bias ]\u003c/tt\u003e"
            }
          ],
          "value": "To be exposed to this issue an MX VC needs to be configured with locality bias as follows:\n\n[ virtual-chassis locality-bias ]"
        }
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      "datePublic": "2026-07-08T16:00:00.000Z",
      "descriptions": [
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              "value": "An Unchecked Input for Loop Condition 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).\u003cp\u003e\u003cspan style=\"background-color: rgb(255, 255, 255);\"\u003eMicro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a \u003cspan style=\"background-color: rgb(255, 255, 255);\"\u003eVirtual-Chassis (VC) scenario with\u0026nbsp;locality\u2011bias configured,\u0026nbsp;\u003c/span\u003eprocessing takes a significant amount of time for each event.\u0026nbsp;If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage.\u003c/span\u003e\u003cbr\u003e\u003c/p\u003e\u003cp\u003eThis issue only affects MX series FPCs up to and including MPC9. It does not affect MPC10/11, LC4800/9600 and MX304.\u003c/p\u003e\u003cp\u003eThis issue affects Junos OS on MX Series:\u003cbr\u003e\u003c/p\u003e\u003cul\u003e\u003cli\u003eall versions before 23.2R2-S7,\u003c/li\u003e\u003cli\u003e23.4 versions before 23.4R2-S8,\u003c/li\u003e\u003cli\u003e24.2 versions before 24.2R2-S4,\u003c/li\u003e\u003cli\u003e24.4 versions before 24.4R2-S3,\u003c/li\u003e\u003cli\u003e25.2 versions before 25.2R2.\u003c/li\u003e\u003c/ul\u003e\u003cbr\u003e\u003cp\u003e\u003c/p\u003e"
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          "value": "An Unchecked Input for Loop Condition 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).Micro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a Virtual-Chassis (VC) scenario with\u00a0locality\u2011bias configured,\u00a0processing takes a significant amount of time for each event.\u00a0If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage.\n\n\nThis issue only affects MX series FPCs up to and including MPC9. It does not affect MPC10/11, LC4800/9600 and MX304.\n\nThis issue affects Junos OS on MX Series:\n\n\n  *  all versions before 23.2R2-S7,\n  *  23.4 versions before 23.4R2-S8,\n  *  24.2 versions before 24.2R2-S4,\n  *  24.4 versions before 24.4R2-S3,\n  *  25.2 versions before 25.2R2."
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      "exploits": [
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              "value": "Juniper SIRT is not aware of any malicious exploitation of this vulnerability."
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      "metrics": [
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            "userInteraction": "NONE",
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            "privilegesRequired": "NONE",
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              "description": "CWE-606 Unchecked Input for Loop Condition",
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      "providerMetadata": {
        "dateUpdated": "2026-07-09T21:03:00.614Z",
        "orgId": "8cbe9d5a-a066-4c94-8978-4b15efeae968",
        "shortName": "juniper"
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          "tags": [
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          "url": "https://supportportal.juniper.net/JSA110075"
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              "value": "The following software releases have been updated to resolve this specific issue:\n\nJunos OS: 23.2R2-S7, 23.4R2-S8, 24.2R2-S4, 24.4R2-S3, 25.2R2, 25.4R1, and all subsequent releases."
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      "source": {
        "advisory": "JSA110075",
        "defect": [
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        "discovery": "USER"
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      "title": "Junos OS: MX Series: In a VC scenario a high rate of micro-BFD session flaps will cause an FPC crash",
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              "value": "To reduce the risk of exploitation, configure BFD with an increased holddown-timer, so that the queued events can be processed before a new up event occurs:\u003cbr\u003e\u003cbr\u003e\u003ctt\u003e[ ... bfd-liveness-detection\u0026nbsp;holddown-interval milliseconds \u0026lt;value\u0026gt; ]\u003c/tt\u003e\u003cbr\u003e\u003cdiv\u003e\u003cbr\u003e\u003c/div\u003e"
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          "value": "To reduce the risk of exploitation, configure BFD with an increased holddown-timer, so that the queued events can be processed before a new up event occurs:\n\n[ ... bfd-liveness-detection\u00a0holddown-interval milliseconds \u003cvalue\u003e ]"
        }
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    "assignerShortName": "juniper",
    "cveId": "CVE-2026-33800",
    "datePublished": "2026-07-09T21:03:00.614Z",
    "dateReserved": "2026-03-23T19:46:13.673Z",
    "dateUpdated": "2026-07-09T21:03:00.614Z",
    "state": "PUBLISHED"
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  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.