# CVE-2026-62866: Dasel: Selector lexer panics on trailing whitespace in `parseCurRune`

> A remote attacker can cause a denial of service by providing a selector with trailing whitespace, triggering a panic in the Dasel library.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Sep 2026
- **Updated:** 21 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-62866, GHSA-65gg-g7rw-6cpc, GO-2026-6548, UBUNTU-CVE-2026-62866

## What is CVE-2026-62866?

CVE-2026-62866 is a medium-severity denial of service vulnerability in TomWright dasel, published on 21 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Dasel is a command-line tool and library for querying, modifying, and transforming data structures. From 3.0.0 until 3.11.2, selector/lexer/tokenize.go parseCurRune advances the input index across trailing whitespace and then reads the source at the exhausted index without an end-of-input check. A selector ending in whitespace, including input passed through lexer.NewTokenizer(...).Tokenize() or dasel.Query, can therefore cause an index-out-of-range panic and terminate the process. This issue is fixed in version 3.11.2.

Weakness: CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2026-62866?

5 open source packages ship an affected version, including github.com/tomwright/dasel/v3, github.com/tomwright/dasel and github.com/tomwright/dasel/v2.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/tomwright/dasel/v3` | Go | From 3.0.0 | 3.11.2 |
| `github.com/tomwright/dasel/v3` | Go | From 3.0.0 | 3.11.2 |
| `github.com/tomwright/dasel/v3` | Go | From 3.0.0 | 3.11.2 |
| `github.com/tomwright/dasel` | Go | All versions | None |
| `github.com/tomwright/dasel/v2` | Go | All versions | None |

## How do I fix CVE-2026-62866?

Upgrade github.com/tomwright/dasel/v3 to 3.11.2 or later.

## Is CVE-2026-62866 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-62866 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-62866 and fix it if it is affected.

What it is: CVE-2026-62866 is a medium-severity denial of service vulnerability in TomWright dasel, published on 21 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-62866 exists.

Affected packages and fixed versions:
- github.com/tomwright/dasel/v3 (Go): affected from 3.0.0; fixed in 3.11.2
- github.com/tomwright/dasel/v3 (Go): affected from 3.0.0; fixed in 3.11.2
- github.com/tomwright/dasel/v3 (Go): affected from 3.0.0; fixed in 3.11.2
- github.com/tomwright/dasel (Go): affected all versions; no fix listed
- github.com/tomwright/dasel/v2 (Go): affected all versions; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-62866/ (Markdown: https://insights.sbomify.com/CVE-2026-62866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-62866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-62866
- OSV: https://osv.dev/vulnerability/CVE-2026-62866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-62866/
Summaries are generated and may contain mistakes; the official description above is the record.