# CVE-2026-33487: goxmldsig has validateSignature Loop Variable Capture Signature Bypass

> Attackers can bypass XML digital signature validation in goxmldsig due to a loop variable capture bug, allowing forged signatures to be accepted.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Mar 2026
- **Updated:** 9 Sep 2026
- **Also known as:** CLEANSTART-2026-TW34089, CLEANSTART-2026-VA24082, CLEANSTART-2026-WK71249, GHSA-479m-364c-43vc, GO-2026-4753, MINI-2h4j-p74g-qr9p, MINI-35rh-257w-3rgx, MINI-446w-6v3c-rv67, MINI-62mf-h9q4-7m9c, MINI-66m6-7gwr-h6hp, MINI-6j5f-2p48-5h24, MINI-75jx-x4w5-7v97, MINI-7gh4-ff93-m429, MINI-7w27-m868-32vj, MINI-8wfh-rgmw-gp6x, MINI-95f7-7hhq-cv3f, MINI-9qpr-82gc-9wjf, MINI-ccf6-594f-c857, MINI-crrw-fvcw-xjfm, MINI-f8xw-rw74-6fg9, MINI-fj69-8pg9-6p45, MINI-gcc6-3372-wgqf, MINI-h8rc-fx3v-2j4r, MINI-hv8j-234p-85gc, MINI-jj45-h9rx-3p3h, MINI-mrgc-367w-wx2x, MINI-wc4h-3fc6-hrxc, MINI-xx72-wm4v-5f5c, MINI-xxcr-9rf2-8m54, ROOT-APP-GOBINARY-CVE-2026-33487

## What is CVE-2026-33487?

CVE-2026-33487 is a high-severity vulnerability in russellhaering goxmldsig, published on 26 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

goxmlsig provides XML Digital Signatures implemented in Go. Prior to version 1.6.0, the `validateSignature` function in `validate.go` goes through the references in the `SignedInfo` block to find one that matches the signed element's ID. In Go versions before 1.22, or when `go.mod` uses an older version, there is a loop variable capture issue. The code takes the address of the loop variable `_ref` instead of its value. As a result, if more than one reference matches the ID or if the loop logic is incorrect, the `ref` pointer will always end up pointing to the last element in the `SignedInfo.References` slice after the loop. goxmlsig version 1.6.0 contains a patch.

Weakness: CWE-682 (Incorrect Calculation), CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-33487?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/russellhaering/goxmldsig` | Go | All versions | 1.6.0 |
| `github.com/russellhaering/goxmldsig` | Go | All versions | 1.6.0 |
| `github.com/russellhaering/goxmldsig` | Go | All versions | 1.6.0 |

Products: Goxmldsig Project Goxmldsig.

## How do I fix CVE-2026-33487?

Upgrade github.com/russellhaering/goxmldsig to 1.6.0 or later.

## Is CVE-2026-33487 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33487 exists.

## Other vulnerabilities in russellhaering goxmldsig

- [CVE-2020-7711](https://insights.sbomify.com/CVE-2020-7711/): Denial of Service (DoS) (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33487 and fix it if it is affected.

What it is: CVE-2026-33487 is a high-severity vulnerability in russellhaering goxmldsig, published on 26 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33487 exists.

Affected packages and fixed versions:
- github.com/russellhaering/goxmldsig (Go): affected all versions; fixed in 1.6.0
- github.com/russellhaering/goxmldsig (Go): affected all versions; fixed in 1.6.0
- github.com/russellhaering/goxmldsig (Go): affected all versions; fixed in 1.6.0

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-2026-33487/ (Markdown: https://insights.sbomify.com/CVE-2026-33487/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33487
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33487
- OSV: https://osv.dev/vulnerability/CVE-2026-33487

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33487/
Summaries are generated and may contain mistakes; the official description above is the record.