CVE-2021-21739
Description
Physical attackers can replace an authenticated optical module with an unauthenticated one in ZTE's ZXCTN 6120H, bypassing authentication and affecting signal transmission.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Physical attackers can replace an authenticated optical module with an unauthenticated one in ZTE's ZXCTN 6120H, bypassing authentication and affecting signal transmission.
Vulnerability
A security vulnerability exists in ZTE's ZXCTN 6120H, a transport network access layer device, version V5.10.00B24. The system does not sufficiently verify data reliability, allowing attackers with physical access to replace an authenticated optical module with an unauthenticated one, bypassing system authentication and detection [1].
Exploitation
An attacker requires physical access to the equipment to swap the optical module. No authentication is needed for this replacement, and the system fails to detect the unauthenticated module [1].
Impact
Successful exploitation affects signal transmission, leading to a low availability impact. The CVSS 3.1 base score is 2.6 (AV:P/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L) [1].
Mitigation
The vulnerability is fixed in version V5.10.00B27 of the ZXCTN 6120H. Users should upgrade to this version to mitigate the issue [1].
AI Insight generated on May 27, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
2- ZTE/transport network access layerdescription
- Range: V5.10.00B24
Patches
0No patches discovered yet.
Vulnerability mechanics
No source-code context for this CVE — mechanics is only generated when we can read the actual fix diff. Without that, the four sections (root cause, attack vector, affected code, fix) would be speculation rather than analysis.
References
1- support.zte.com.cn/support/news/LoopholeInfoDetail.aspxmitrex_refsource_MISC
News mentions
0No linked articles in our index yet.