CVE-2021-0227Network attack vector

Service crashes via crafted HTTP packet processing

Published Apr 22, 2021 · Updated Sep 16, 2024

Buffer-bounds failure in J-Web in Juniper Networks Junos OS on SRX Series allows remote attackers to crash services via crafted HTTP packets. J-Web processes attacker-controlled HTTP packets without adequate memory-buffer bounds restrictions; Juniper has not disclosed the affected function or exact invalid operation. Unauthenticated network access to web management, web-management HTTPS, or dynamic VPN is sufficient, and repeated packets sustain crashes of web-management, ntpd, and L2CPD.

CVSS severity7.5
High
EPSS probability1.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer-bounds failure in J-Web in Juniper Networks Junos OS on SRX Series allows remote attackers to crash services via crafted HTTP packets. J-Web processes attacker-controlled HTTP packets without adequate memory-buffer bounds restrictions; Juniper has not disclosed the affected function or exact invalid operation. Unauthenticated network access to web management, web-management HTTPS, or dynamic VPN is sufficient, and repeated packets sustain crashes of web-management, ntpd, and L2CPD.

The record

CVE
CVE-2021-0227
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-119, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=17.3 <17.3R3-S9
  2. Affected versionversion=17.4 <17.4R2-S11, 17.4R3-S2
  3. Affected versionversion=18.2 <18.2R3-S5
  4. Affected versionversion=18.3 <18.3R2-S4, 18.3R3-S3
  5. Affected versionversion=18.4 <18.4R2-S5, 18.4R3-S4
  6. Affected versionversion=19.1 <19.1R3-S2
  7. Affected versionversion=19.2 <19.2R1-S5, 19.2R3
  8. Affected versionversion=19.3 <19.3R3
  9. Affected versionversion=19.4 <19.4R2-S1, 19.4R3
  10. Affected versionversion=20.1 <20.1R1-S2, 20.1R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.3 <17.3R3-S9; version=17.4 <17.4R2-S11, 17.4R3-S2; version=18.2 <18.2R3-S5; version=18.3 <18.3R2-S4, 18.3R3-S3; version=18.4 <18.4R2-S5, 18.4R3-S4; version=19.1 <19.1R3-S2; version=19.2 <19.2R1-S5, 19.2R3; version=19.3 <19.3R3; version=19.4 <19.4R2-S1, 19.4R3; version=20.1 <20.1R1-S2, 20.1R2

Published CVSS scores

7.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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