# CVE-2026-57957: Papermark 0.22.0 - CORS Misconfiguration in Viewer Upload Endpoint

> Attackers can exploit CORS misconfiguration to upload files and read data from victim datarooms via credentialed cross-origin requests.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 29 Jun 2026
- **Updated:** 14 Jul 2026
- **Also known as:** GHSA-4cq7-5c7c-cc5r

## What is CVE-2026-57957?

CVE-2026-57957 is a low-severity vulnerability in papermark, published on 29 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Papermark through 0.22.0 contains a cross-origin resource sharing (CORS) misconfiguration vulnerability that allows unauthenticated remote attackers to perform credentialed cross-origin requests by exploiting the TUS-based viewer upload endpoint reflecting arbitrary request Origins with Access-Control-Allow-Credentials set to true. Attackers can lure authenticated victims to malicious pages that silently issue credentialed cross-origin requests to upload arbitrary files into victim datarooms and read credentialed responses.

Weakness: CWE-942 (Permissive Cross-domain Security Policy with Untrusted Domains)

## Which versions are affected by CVE-2026-57957?


## How do I fix CVE-2026-57957?

No fix has been published for CVE-2026-57957 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-57957 being exploited?

There is no known exploitation of CVE-2026-57957 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57957 and fix it if it is affected.

What it is: CVE-2026-57957 is a low-severity vulnerability in papermark, published on 29 Jun 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-57957 in the wild and no public exploit code.

Affected product: papermark. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-57957/ (Markdown: https://insights.sbomify.com/CVE-2026-57957/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57957
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57957
- OSV: https://osv.dev/vulnerability/CVE-2026-57957

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-57957/
Summaries are generated and may contain mistakes; the official description above is the record.