CVE-2026-21907Network attack vector

Traffic disclosure via static-key TLS ciphers

Published Jan 15, 2026 · Updated Jan 15, 2026

Weak cryptography in Juniper Networks Junos Space before 24.1R5 allows man-in-the-middle attackers with server key material to read TLS traffic. The Apache HTTPS endpoint advertises and negotiates RSA static-key cipher suites instead of requiring ephemeral key exchange with Perfect Forward Secrecy. Exploitation requires an on-path position and access to the server's private key; recorded sessions can then be decrypted, while integrity and availability remain unaffected.

CVSS severity8.2
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Weak cryptography in Juniper Networks Junos Space before 24.1R5 allows man-in-the-middle attackers with server key material to read TLS traffic. The Apache HTTPS endpoint advertises and negotiates RSA static-key cipher suites instead of requiring ephemeral key exchange with Perfect Forward Secrecy. Exploitation requires an on-path position and access to the server's private key; recorded sessions can then be decrypted, while integrity and availability remain unaffected.

The record

CVE
CVE-2026-21907
Published
Jan 15, 2026
Updated
Jan 15, 2026
Vendor
Juniper Networks
Product
Junos Space
Classifications
CWE-327, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 15, 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=0 <24.1R5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos Spaceversion=0 <24.1R5

Published CVSS scores

7.5Juniper NetworksCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
8.2Juniper NetworksCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:L/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-327Use of a Broken or Risky Cryptographic Algorithm
T1557Adversary-in-the-Middle

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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