# OSV-2026-204: Segv on unknown address in icalarray_append

> A segmentation fault in the iCalendar library's array append function can cause a denial of service when parsing malformed vCard data.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Feb 2026

## What is OSV-2026-204?

OSV-2026-204 is a memory corruption vulnerability in libical, published on 6 Feb 2026. 

### Official description

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=481635423

```
Crash type: Segv on unknown address
Crash state:
icalarray_append
icalstrarray_append
_parse_vcard
```

## Which versions are affected by OSV-2026-204?

1 open source package ship an affected version, including libical.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libical` | OSS-Fuzz | All versions | None |

## How do I fix OSV-2026-204?

No fix has been published for OSV-2026-204 yet. Limit exposure of the affected software until one is available.

## Is OSV-2026-204 being exploited?

There is no known exploitation of OSV-2026-204 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for OSV-2026-204 and fix it if it is affected.

What it is: OSV-2026-204 is a memory corruption vulnerability in libical, published on 6 Feb 2026. 
Exploitation: There is no known exploitation of OSV-2026-204 in the wild and no public exploit code.

Affected packages and fixed versions:
- libical (OSS-Fuzz): 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/OSV-2026-204/ (Markdown: https://insights.sbomify.com/OSV-2026-204/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/OSV-2026-204

---
From sbomify Insights: https://insights.sbomify.com/OSV-2026-204/
Summaries are generated and may contain mistakes; the official description above is the record.