# CVE-2026-62866: Dasel selector lexer panic on trailing whitespace

Source: https://junglewise.ai/threats/cve-2026-62866-dasel-selector-lexer-panic-on-trailing-whitespace  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-21. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-62866 · Severity: medium · CVSS 6.2 · Published 2026-09-21

Dasel is a library and CLI tool for querying and modifying structured data formats like JSON. An attacker can crash the process by providing a selector query with trailing whitespace, causing an uncontrolled panic that disrupts service availability. This affects any application using Dasel to parse untrusted selector inputs.

Technologies: [github.com/tomwright/dasel (Go)](https://junglewise.ai/threats/technologies/github-com-tomwright-dasel), [github.com/tomwright/dasel/v2 (Go)](https://junglewise.ai/threats/technologies/github-com-tomwright-dasel-v2), [github.com/tomwright/dasel/v3 (Go)](https://junglewise.ai/threats/technologies/github-com-tomwright-dasel-v3). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-62866 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-62866 being exploited in the wild.

**How severe is CVE-2026-62866?** Medium severity, with a CVSS score of 6.2, published 21 September 2026.

**Which products and versions are affected?** github.com/tomwright/dasel (Go) SEMVER:introduced=0; github.com/tomwright/dasel/v2 (Go) SEMVER:introduced=0; github.com/tomwright/dasel/v3 (Go) >= 3.0.0, < 3.11.2, SEMVER:introduced=3.0.0,fixed=3.11.2.

**Is there a fix for CVE-2026-62866?** Yes. github.com/tomwright/dasel/v3 (Go): upgrade to 3.11.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-62866 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-62866?** Check whether you run github.com/tomwright/dasel (Go), github.com/tomwright/dasel/v2 (Go) or github.com/tomwright/dasel/v3 (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/tomwright/dasel/v3 (Go): upgrade to 3.11.2 or later

  ```sh
  go get github.com/tomwright/dasel/v3@v3.11.2
  ```


## Technical details

The vulnerability is a panic (runtime error: index out of range) in the selector lexer's `parseCurRune()` function in `selector/lexer/tokenize.go`. The whitespace-skipping loop (lines 55–57) advances the position pointer `p.i` to `p.srcLen` when encountering trailing whitespace, but the subsequent line 60 reads `p.src[p.i]` without bounds checking. This allows the parser to access memory outside the input string bounds. The vulnerability is reachable directly via the library API (`dasel.Query()`) or indirectly through the CLI tool with any selector ending in whitespace (e.g., `'a '`, `'   '`, `'a\t'`, `'a + '`). No authentication or user interaction is required; only network reachability to an application using Dasel for untrusted selector input parsing.

## Affected products

- Tom Wright Dasel v3.x (all versions through v3.11.0)

## Identifiers

- CVE-2026-62866
- GHSA-65gg-g7rw-6cpc
- GO-2026-6548

## Timeline

- 2026-09-22: disclosed
- 2026-09-22: advisory: GHSA-65gg-g7rw-6cpc published

## Related threats

- [Dasel unbounded recursion in JSON and XML readers causes stack overflow DoS](https://junglewise.ai/threats/cve-2026-59168-dasel-unbounded-recursion-in-json-and-xml-readers-causes-stack)
- [TomWright Dasel infinite loop in selector lexer](https://junglewise.ai/threats/cve-2026-46378-tomwright-dasel-infinite-loop-in-selector-lexer)
- [TomWright Dasel index out of bounds panic in selector lexer](https://junglewise.ai/threats/cve-2026-46377-tomwright-dasel-index-out-of-bounds-panic-in-selector-lexer)
- [Dasel has unbounded YAML alias expansion in dasel leads to CPU/memory denial of service](https://junglewise.ai/threats/cve-2026-33320-dasel-has-unbounded-yaml-alias-expansion-in-dasel-leads-to-cpu)