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Unrated severityNVD Advisory· Published Jul 17, 2023· Updated Oct 21, 2024

CVE-2023-34140

CVE-2023-34140

Description

A buffer overflow vulnerability in the Zyxel ATP series firmware versions 4.32 through 5.36 Patch 2, USG FLEX series firmware versions 4.50 through 5.36 Patch 2, USG FLEX 50(W) series firmware versions 4.16 through 5.36 Patch 2, USG20(W)-VPN series firmware versions 4.16 through 5.36 Patch 2, VPN series firmware versions 4.30 through 5.36 Patch 2, NXC2500 firmware versions 6.10(AAIG.0) through 6.10(AAIG.3), and NXC5500 firmware versions 6.10(AAOS.0) through 6.10(AAOS.4), could allow an unauthenticated, LAN-based attacker to cause denial of service (DoS) conditions by sending a crafted request to the CAPWAP daemon.

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

A buffer overflow vulnerability in Zyxel ATP, USG FLEX, VPN, NXC series devices allows an unauthenticated LAN attacker to cause denial of service by sending a crafted request to the CAPWAP daemon.

Vulnerability

A buffer overflow vulnerability exists in the CAPWAP daemon of multiple Zyxel devices, including ATP series (firmware versions 4.32 through 5.36 Patch 2), USG FLEX series (versions 4.50 through 5.36 Patch 2), USG FLEX 50(W) series (versions 4.16 through 5.36 Patch 2), USG20(W)-VPN series (versions 4.16 through 5.36 Patch 2), VPN series (versions 4.30 through 5.36 Patch 2), NXC2500 (versions 6.10(AAIG.0) through 6.10(AAIG.3)), and NXC5500 (versions 6.10(AAOS.0) through 6.10(AAOS.4)) [1]. The flaw occurs when a crafted request is processed, leading to a buffer overflow.

Exploitation

An unauthenticated attacker with LAN access can send a specially crafted request to the affected device's CAPWAP daemon to trigger the buffer overflow [1]. No authentication or user interaction is required to exploit this vulnerability.

Impact

Successful exploitation causes denial of service (DoS) conditions on the target device, potentially making it unresponsive or causing crashes [1]. No confidentiality or integrity impact is described.

Mitigation

Zyxel has released firmware updates to address this vulnerability. Users should update to the latest versions for their respective devices as indicated in the advisory [1]. No workarounds are provided. All affected versions are listed in the advisory.

References
  1. Zyxel security advisory for multiple vulnerabilities in firewalls and WLAN controllers | Zyxel Networks

AI Insight generated on May 26, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

7
  • Zyxel/ATP seriescpe-rescue
    Range: 4.32 through 5.36 Patch 2
  • Zyxel/NXC2500 firmwarev5
    Range: 6.10(AAIG.0) through 6.10(AAIG.3)
  • Zyxel/NXC5500 firmwarev5
    Range: 6.10(AAOS.0) through 6.10(AAOS.4)
  • Zyxel/USG20(W)-VPN seriescpe-rescue
    Range: 4.16 through 5.36 Patch 2
  • Zyxel/USG FLEX seriescpe-rescue2 versions
    4.16 through 5.36 Patch 2+ 1 more
    • (no CPE)range: 4.16 through 5.36 Patch 2
    • (no CPE)range: 4.50 through 5.36 Patch 2
  • Zyxel/VPN seriescpe-rescue
    Range: 4.30 through 5.36 Patch 2

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

1

News mentions

0

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