CVE-2026-57021Network attack vector

Unauthenticated service disruption via http-gk out-of-bounds write

Published Jul 9, 2026 · Updated Jul 9, 2026

Out-of-bounds write in Juniper Networks Junos OS on SRX Series allows remote attackers to crash http-gk with crafted VPN requests. Specifically formatted pre-logon compliance-check requests cause http-gk to write beyond a memory buffer and terminate. Remote-access VPN with pre-logon compliance checking must be configured; J-Web, VPN, and firewall authentication remain unavailable until http-gk automatically restarts.

CVSS severity6.9
Medium
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Juniper Networks Junos OS on SRX Series allows remote attackers to crash http-gk with crafted VPN requests. Specifically formatted pre-logon compliance-check requests cause http-gk to write beyond a memory buffer and terminate. Remote-access VPN with pre-logon compliance checking must be configured; J-Web, VPN, and firewall authentication remain unavailable until http-gk automatically restarts.

The record

CVE
CVE-2026-57021
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-787, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record 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=23.2 <23.2R2-S7
  2. Affected versionversion=23.4 <23.4R2-S8
  3. Affected versionversion=24.2 <24.2R2-S4
  4. Affected versionversion=24.4 <24.4R2-S4
  5. Affected versionversion=25.2 <25.2R2
  6. Affected versionversion=25.4 <25.4R1-S1, 25.4R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=23.2 <23.2R2-S7; version=23.4 <23.4R2-S8; version=24.2 <24.2R2-S4; version=24.4 <24.4R2-S4; version=25.2 <25.2R2; version=25.4 <25.4R1-S1, 25.4R2

Published CVSS scores

5.3Juniper Networks, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
6.9Juniper Networks, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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-787Out-of-bounds Write
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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