# GO-2026-5781: Uncatchable stack-overflow denial of service in rsc.io/pdf

> Attackers can crash services parsing untrusted PDFs using rsc.io/pdf by sending deeply nested documents that cause uncatchable stack overflows.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Jul 2026

## What is GO-2026-5781?

GO-2026-5781 is a denial of service vulnerability in rsc.io/pdf, published on 27 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

pdf.Open and PDF object resolution in rsc.io/pdf recurse without bound on nested arrays and dictionaries. A sufficiently deeply nested document exhausts the goroutine stack limit and triggers a fatal, uncatchable stack overflow. Any service that parses untrusted PDFs with rsc.io/pdf can therefore be taken down by a single small input.

## Which versions are affected by GO-2026-5781?

1 open source package ship an affected version, including rsc.io/pdf.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `rsc.io/pdf` | Go | All versions | None |

## How do I fix GO-2026-5781?

No fix has been published for GO-2026-5781 yet. Limit exposure of the affected software until one is available.

## Is GO-2026-5781 being exploited?

There is no known exploitation of GO-2026-5781 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GO-2026-5781 and fix it if it is affected.

What it is: GO-2026-5781 is a denial of service vulnerability in rsc.io/pdf, published on 27 Jul 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 GO-2026-5781 in the wild and no public exploit code.

Affected packages and fixed versions:
- rsc.io/pdf (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/GO-2026-5781/ (Markdown: https://insights.sbomify.com/GO-2026-5781/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GO-2026-5781

---
From sbomify Insights: https://insights.sbomify.com/GO-2026-5781/
Summaries are generated and may contain mistakes; the official description above is the record.