CVE-2025-35435VulnerabilityPublished 17 Sep 2025Updated 30 Sep 2025

CVE-2025-35435: CISA Thorium · Divide By Zero

Affects CISA ThoriumSource CVE Database V5

Not known to be exploited · CVSS 4.3 Medium.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

4.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 37% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 2025
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 2026-10-25.

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 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

Affected software

Product	Affected	Fixed in
CISA Thorium	Affected =1.0.0	Fixed in–

AI-suggested

1. Apply the patch or update to the fixed version of CISA Thorium that includes commit 89101a6 to eliminate the divide-by-zero flaw. 2. Restrict and monitor authenticated access to the Thorium service, enforcing strong authentication mechanisms and least privilege principles to reduce the risk of malicious insiders or compromised accounts exploiting the vulnerability. 3. Implement robust logging and alerting on abnormal service crashes or restarts to detect potential exploitation attempts promptly. 4. Conduct regular security audits and vulnerability scans on Thorium deployments to ensure no outdated versions remain in production. 5. Consider deploying application-layer protections such as input validation or filtering to prevent zero values from being accepted as stream split sizes if patching is delayed. 6. Establish incident response procedures to quickly recover from service disruptions caused by this vulnerability.

Description

CISA Thorium accepts a stream split size of zero then divides by this value. A remote, authenticated attacker could cause the service to crash. Fixed in commit 89101a6.

Impact

For European organizations using CISA Thorium 1.0.0, this vulnerability poses a risk of service disruption due to denial of service attacks by authenticated users. While the impact is limited to availability and does not compromise data confidentiality or integrity, the crash of Thorium services could interrupt critical cybersecurity monitoring or response functions if Thorium is integrated into security operations. Organizations relying heavily on Thorium for threat detection or incident response may experience operational delays or gaps in security coverage during service downtime. The requirement for authentication limits the attack surface to insiders or compromised accounts, but insider threats or credential theft could still enable exploitation. Given the medium severity and the availability of a fix, timely patching is essential to maintain service reliability and avoid potential operational disruptions.

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Oct 2025, 00:17 UTC

WeaknessesCWE-369

Technical details

References

Community reviews

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