# CVE-2026-23831: Rekor COSE v0.0.1 Canonicalize crashes when passed empty Message

> An attacker can cause a panic in Rekor by submitting a malformed COSE entry with an empty message, resulting in a temporary service disruption.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Jan 2026
- **Updated:** 23 Jan 2026
- **Also known as:** CLEANSTART-2026-DO33187, CLEANSTART-2026-RI42866, DEBIAN-CVE-2026-23831, GHSA-273p-m2cw-6833, GO-2026-4354, MINI-299f-xvhq-vgpp, MINI-4885-c5jf-xj4f, MINI-4j5w-fcr3-8mr5, MINI-567h-vvvr-5h8w, MINI-6qw9-5vr8-r8hm, MINI-8746-q95f-f4mx, MINI-8958-pjf7-j627, MINI-977x-x2mx-723m, MINI-9pqh-jpjq-f2q6, MINI-9rqp-vr67-3rjg, MINI-fpqp-xp5m-5r2f, MINI-g468-8ccw-qh6c, MINI-g6hc-gv44-mg2w, MINI-gv3r-9x35-9cg2, MINI-jcj6-rjr9-qcwp, MINI-jcqm-24rp-crgc, MINI-jf74-3q4p-r2c6, MINI-mg34-4hm2-678p, MINI-mp5p-ggcg-vg74, MINI-v42g-4496-3fcq, MINI-v526-5957-gccm, MINI-xfqv-3mq2-ppv4, MINI-xrh4-3m2j-mx5c, UBUNTU-CVE-2026-23831

## What is CVE-2026-23831?

CVE-2026-23831 is a medium-severity vulnerability in sigstore rekor, published on 22 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Rekor is a software supply chain transparency log. In versions 1.4.3 and below, the entry implementation can panic on attacker-controlled input when canonicalizing a proposed entry with an empty spec.message, causing nil Pointer Dereference. Function validate() returns nil (success) when message is empty, leaving sign1Msg uninitialized, and Canonicalize() later dereferences v.sign1Msg.Payload. A malformed proposed entry of the cose/v0.0.1 type can cause a panic on a thread within the Rekor process. The thread is recovered so the client receives a 500 error message and service still continues, so the availability impact of this is minimal. This issue has been fixed in version 1.5.0.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-23831?

3 open source packages ship an affected version, including github.com/sigstore/rekor. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/sigstore/rekor` | Go | All versions | 1.5.0 |
| `github.com/sigstore/rekor` | Go | All versions | 1.5.0 |
| `github.com/sigstore/rekor` | Go | All versions | 1.5.0 |

Products: Linuxfoundation Rekor.

## How do I fix CVE-2026-23831?

Upgrade github.com/sigstore/rekor to 1.5.0 or later.

## Is CVE-2026-23831 being exploited?

There is no known exploitation of CVE-2026-23831 in the wild and no public exploit code.

## Other vulnerabilities in sigstore rekor

- [CVE-2023-30551](https://insights.sbomify.com/CVE-2023-30551/): Rekor's compressed archives can result in OOM conditions (high 7.5)
- [CVE-2026-24117](https://insights.sbomify.com/CVE-2026-24117/): Rekor affected by Server-Side Request Forgery (SSRF) via provided public key URL (medium 5.3)
- [CVE-2023-33199](https://insights.sbomify.com/CVE-2023-33199/): malformed proposed intoto v0.0.2 entries can cause a panic in Rekor (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23831 and fix it if it is affected.

What it is: CVE-2026-23831 is a medium-severity vulnerability in sigstore rekor, published on 22 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-23831 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/sigstore/rekor (Go): affected all versions; fixed in 1.5.0
- github.com/sigstore/rekor (Go): affected all versions; fixed in 1.5.0
- github.com/sigstore/rekor (Go): affected all versions; fixed in 1.5.0

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-2026-23831/ (Markdown: https://insights.sbomify.com/CVE-2026-23831/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23831
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23831
- OSV: https://osv.dev/vulnerability/CVE-2026-23831

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23831/
Summaries are generated and may contain mistakes; the official description above is the record.