VulnerabilityPublished 20 Sep 2022Updated 29 May 2025

CVE-2022-34746: Zyxel GS1900 series firmware · Insufficient Entropy

Affects Zyxel GS1900 series firmwareSource CVE Database V5

Not known to be exploited · CVSS 5.9 Medium : upgrade to V2.70 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in V2.70

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Sep 2022
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Zyxel GS1900 series firmware to V2.70.

Affected software

Product	Affected	Fixed in
Zyxel Zyxel GS1900 series firmware	Affected <V2.70	Fixed in V2.70

AI-suggested

Immediate firmware upgrade: Organizations should verify their Zyxel GS1900 firmware version and upgrade to version 2.70 or later, where this vulnerability is addressed.
If immediate upgrade is not possible, restrict access to the web administration interface by implementing network segmentation and firewall rules to limit management access only to trusted hosts and networks.
Employ additional layers of security such as VPN tunnels or secure management gateways to protect administrative traffic.
Monitor network traffic for unusual activity targeting the management interface, including attempts to retrieve certificates or perform cryptanalysis.
Encourage Zyxel to provide patches or updated firmware with improved entropy sources for RSA key generation.
Consider replacing affected devices with models or vendors that follow best cryptographic practices if long-term support is uncertain.
Conduct regular security audits and penetration tests focusing on network device management interfaces to detect similar weaknesses.
Educate network administrators about the risks of weak cryptographic implementations and the importance of timely patching.

Description

An insufficient entropy vulnerability caused by the improper use of randomness sources with low entropy for RSA key pair generation was found in Zyxel GS1900 series firmware versions prior to V2.70. This vulnerability could allow an unauthenticated attacker to retrieve a private key by factoring the RSA modulus N in the certificate of the web administration interface.

Impact

For European organizations using Zyxel GS1900 series switches, this vulnerability poses a significant risk to the confidentiality of their network management interfaces. An attacker who can factor the RSA modulus can obtain the private key, potentially allowing them to intercept or decrypt administrative sessions, perform man-in-the-middle attacks, or impersonate the device's management interface. This could lead to unauthorized configuration changes, exposure of sensitive network topology information, or further lateral movement within the network. Since the vulnerability does not affect integrity or availability directly, the primary concern is confidentiality breach. Given that many European enterprises and service providers deploy Zyxel network equipment in their infrastructure, especially in small to medium-sized businesses and branch offices, the risk is non-trivial. The requirement for high attack complexity somewhat limits exploitation, but the lack of authentication and user interaction requirements means that a skilled attacker with network access could leverage this vulnerability. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers may develop tools to exploit this weakness. The impact is heightened in regulated industries within Europe, such as finance, healthcare, and critical infrastructure, where confidentiality of network management is paramount.

CWE-331Insufficient Entropy (opens in a new tab)
Base weaknessOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others.
Implementation
Determine the necessary entropy to adequately provide for randomness and predictability. This can be achieved by increasing the number of bits of objects such as keys and seeds.
OWASP Cheat Sheets
Session Management (opens in a new tab)
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
Cryptographic Storage (opens in a new tab)
OWASP ASVS 4.0.3
V3.2.2 (opens in a new tab)
V3.2.4 (opens in a new tab)
V2.3.1 (opens in a new tab)
Attack patterns
Session Credential Falsification through Prediction (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-insufficient-entropy-vulnerability-of-gs1900-series-switches (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 8 Jul 2025, 03:09 UTC

WeaknessesCWE-331

Technical details

References

Community reviews

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