CVE-2026-21907
Published: 15 January 2026
Summary
CVE-2026-21907 is a high-severity Use of a Broken or Risky Cryptographic Algorithm (CWE-327) vulnerability in Juniper Junos Space. Its CVSS base score is 8.2 (High).
Operationally, ranked at the 7.8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-2700
Vulnerability details
A Use of a Broken or Risky Cryptographic Algorithm vulnerability in the TLS/SSL server of Juniper Networks Junos Space allows the use of static key ciphers (ssl-static-key-ciphers), reducing the confidentiality of on-path traffic communicated across the connection. These ciphers also…
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do not support Perfect Forward Secrecy (PFS), affecting the long-term confidentiality of encrypted communications.This issue affects all versions of Junos Space before 24.1R5.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Contacts with security groups provide timely information on broken or risky cryptographic algorithms, reducing the likelihood of their selection and use.
Ongoing education and sharing of recommended practices helps organizations identify and migrate away from broken or risky cryptographic algorithms.
Cross-organization threat feeds commonly include advances in cryptanalysis and active exploits against weak or broken algorithms, allowing organizations to deprecate them proactively.
Capital planning and funding allow selection and ongoing support of strong cryptographic algorithms rather than weak or broken ones.
Risk updates surface newly-broken or risky cryptographic algorithms as threat intelligence and computing advances evolve, enabling timely replacement.
Scanners flag use of broken or weak cryptographic algorithms via known-vulnerability databases.
Enforces approved cryptographic algorithms for each use case, blocking use of broken or risky algorithms.
Flaw remediation replaces broken or risky cryptographic algorithms once safer implementations are released by vendors.