CVE-2026-22321: Stack-Based Buffer Overflow in CLI Login Username Handling over CLI

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-18 · updated 2026-06-17
Weakness: CWE-121

Description

A stack-based buffer overflow in the device's Telnet/SSH CLI login routine occurs when a unauthenticated attacker send an oversized or unexpected username input. An overflow condition crashes the thread handling the login attempt, forcing the session to close. Because other CLI sessions remain unaffected, the impact is limited to a low‑severity availability disruption.

Affected products

Phoenix Contact FL NAT 2008: before 3.53 — fixed in 3.53
Phoenix Contact FL NAT 2208: before 3.53 — fixed in 3.53
Phoenix Contact FL NAT 2304-2GC-2SFP: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2005: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2008: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2008F: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2016: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2105: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2108: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2116: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2204-2TC-2SFX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2205: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2206-2FX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2206-2FX SM: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2206-2FX SM ST: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2206-2FX ST: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2206-2SFX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2206-2SFX PN: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2206C-2FX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2207-FX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2207-FX SM: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2208: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2208 PN: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2208C: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2212-2TC-2SFX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2214-2FX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2214-2FX SM: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2214-2SFX: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2214-2SFX PN: before 3.53 — fixed in 3.53
Phoenix Contact FL SWITCH 2216: before 3.53 — fixed in 3.53

How to fix

Upgrade to a fixed version: Phoenix Contact FL NAT 2008 3.53; Phoenix Contact FL NAT 2208 3.53; Phoenix Contact FL NAT 2304-2GC-2SFP 3.53; Phoenix Contact FL SWITCH 2005 3.53; Phoenix Contact FL SWITCH 2008 3.53; Phoenix Contact FL SWITCH 2008F 3.53; Phoenix Contact FL SWITCH 2016 3.53; Phoenix Contact FL SWITCH 2105 3.53; Phoenix Contact FL SWITCH 2108 3.53; Phoenix Contact FL SWITCH 2116 3.53; Phoenix Contact FL SWITCH 2204-2TC-2SFX 3.53; Phoenix Contact FL SWITCH 2205 3.53. Check the vendor advisory for mitigations.

References

https://certvde.com/de/advisories/VDE-2025-104

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