CVE-2021-21727
Description
A remote attacker can cause denial of service on ZTE ZXHN F623 routers by sending crafted IPv6 packets, affecting all versions up to V6.0.0P3T33.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A remote attacker can cause denial of service on ZTE ZXHN F623 routers by sending crafted IPv6 packets, affecting all versions up to V6.0.0P3T33.
Vulnerability
The vulnerability resides in the IPv6 packet processing of ZTE ZXHN F623 routers. By sending specially constructed IPv6 packets, a remote attacker can trigger an amplification of traffic, leading to device denial of service. All versions up to V6.0.0P3T33 are affected [1].
Exploitation
An attacker needs network access to the target device and the ability to send IPv6 packets. No authentication or user interaction is required. The attacker crafts specific IPv6 packets that cause the device to amplify traffic, eventually exhausting resources and causing a denial of service [1].
Impact
Successful exploitation results in a denial of service condition, rendering the device unavailable. The CVSS v3.1 base score is 8.6 (High) with vector AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H, indicating high availability impact and a changed scope [1].
Mitigation
ZTE has released firmware version V6.0.0P3T34 to fix this vulnerability. Users should update their ZXHN F623 devices to this version or later. No workarounds are mentioned in the advisory [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/ZTEdescription
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.