Thorium: Uncaught Exception
CVE-2025-35436 is a high-severity uncaught exception vulnerability in Thorium from CISA, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 6a65a27 as the first without the flaw, so updating Thorium to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.56% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Thorium to 6a65a27 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 6.9 | Medium | CNA |
| CVSS 3.1 | 5.3 | Medium | CNA |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
CISA Thorium uses '.unwrap()' to handle errors related to account verification email messages. An unauthenticated remote attacker could cause a crash by providing a specially crafted email address or response. Fixed in commit 6a65a27.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Uncaught Exception
An exception is thrown from a function, but it is not caught.
How developers prevent this class of flaw
- The choice between a language which has named or unnamed exceptions needs to be done. While unnamed exceptions exacerbate the chance of not properly dealing with an exception, named exceptions suffer from the up call version of the weak base class problem.
- A language can be used which requires, at compile time, to catch all serious exceptions. However, one must make sure to use the most current version of the API as new exceptions could be added.
- Catch all relevant exceptions. This is the recommended solution. Ensure that all exceptions are handled in such a way that you can be sure of the state of your system at any given moment.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Third-party and government advisories
- raw.githubusercontent.com/cisagov/CSAF/develop/csaf_files/IT/white/2025/va-25-259-01.jsonThird Party Advisory
- cve.org/CVERecord?id=CVE-2025-35436Third Party Advisory
Other vulnerabilities in Thorium
- 9.8 Critical severity
- 8.8 High severity
- 7.5 High severity
Recent Uncaught Exception vulnerabilities
- 7.5 High severity
- 9.2 Critical severity
- 8.7 High severity
- 8.7 High severity
- 7.1 High severity
- 8.7 High severity
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