klever-go: Improper Encoding or Escaping of Output
CVE-2026-82409 is a high-severity improper encoding or escaping of output vulnerability in klever-go from Klever-io, with a CVSS 4.0 base score of 8.4 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected klever-go versions: < 1.7.20. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.34% 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
- Check which version of klever-go you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
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.
- Attack requirements
- NoneThe attack does not depend on a particular deployment or configuration.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Confidentiality (vulnerable system)
- NoneNo loss of confidentiality on the vulnerable system.
- Integrity (vulnerable system)
- HighSerious loss of integrity on the vulnerable system.
- Availability (vulnerable system)
- HighSerious loss of availability on the vulnerable system.
- Confidentiality (other systems)
- NoneNo loss of confidentiality on systems beyond the vulnerable one.
- Integrity (other systems)
- HighSerious loss of integrity on systems beyond the vulnerable one.
- Availability (other systems)
- LowLimited loss of availability on systems beyond the vulnerable one.
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. Scored by CNA (github.com).
Official description
Klever-Go is the Go implementation of the Klever blockchain protocol. Prior to 1.7.20, indexer/common.go serializedDataForUpdateAccounts places the attacker-controlled acc.Name value into an Elasticsearch _bulk JSON and NDJSON request without escaping it. The SetAccountName transaction accepts valid UTF-8 account names containing quotes, backslashes, and newlines, and the resulting name is stored in consensus account state. When an indexer processes the account, those characters can break the JSON string, reject a bulk batch, or inject additional bulk actions that create, overwrite, or delete documents in indices writable by the indexer. The persistent state value is replayed by new or historical indexers, and direct access to the indexing host or Elasticsearch port is not required. This issue is fixed in version 1.7.20.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Encoding or Escaping of Output
The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.
How developers prevent this class of flaw
- Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using the ESAPI Encoding control or a similar tool, library, or framework. These will help the programmer encode outputs in a manner less prone to error. Alternately, use built-in functions, but consider using wrappers in case those functions are discovered to have a vulnerability.
- If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated. For example, stored procedures can enforce database query structure and reduce the likelihood of SQL injection.
- Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies.
More Improper Encoding or Escaping of Output vulnerabilities (CWE-116)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other vulnerabilities in klever-go
- 7.5 High severity
- 8.6 High severity
- 7.0 High severity
- 7.1 High severity
- 8.7 High severity
- 8.7 High severity
Recent Improper Encoding or Escaping of Output vulnerabilities
- 9.8 Critical severity
- 8.7 High severity
- 7.3 High severity
- 7.5 High severity
- 8.1 High severity
- 9.1 Critical severity
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