# CVE-2019-11703: Memory corruption in Thunderbird

> A heap buffer overflow in Thunderbird's iCal parser allows attackers to cause a crash or potentially execute arbitrary code via crafted emails.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Jul 2019
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2019-11703, GHSA-j937-8hgv-v466, UBUNTU-CVE-2019-11703

## What is CVE-2019-11703?

CVE-2019-11703 is a critical memory corruption vulnerability in Mozilla Thunderbird, published on 23 Jul 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw in Thunderbird's implementation of iCal causes a heap buffer overflow in parser_get_next_char when processing certain email messages, resulting in a potentially exploitable crash. This vulnerability affects Thunderbird < 60.7.1.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2019-11703?

It affects 1 product.


Products: Mozilla Thunderbird.

## How do I fix CVE-2019-11703?

Upgrade to a fixed version.

## Is CVE-2019-11703 being exploited?

There is no known exploitation of CVE-2019-11703 in the wild and no public exploit code.

Public exploit code:

- Thunderbird ESR < 60.7.XXX - 'parser_get_next_char' Heap-Based Buffer Overflow (exploitdb)

## Other vulnerabilities in Mozilla Thunderbird

- [CVE-2026-92238](https://insights.sbomify.com/CVE-2026-92238/): Ambiguous parsing of mail headers (critical 9.8)
- [CVE-2026-84637](https://insights.sbomify.com/CVE-2026-84637/): Calendar invitation attachments could launch local executables (critical 9.8)
- [CVE-2021-43529](https://insights.sbomify.com/CVE-2021-43529/): Memory corruption in Thunderbird (critical 9.8)
- [CVE-2019-11704](https://insights.sbomify.com/CVE-2019-11704/): Memory corruption in Thunderbird (critical 9.8)
- [CVE-2019-11705](https://insights.sbomify.com/CVE-2019-11705/): Memory corruption in Thunderbird (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-11703 and fix it if it is affected.

What it is: CVE-2019-11703 is a critical memory corruption vulnerability in Mozilla Thunderbird, published on 23 Jul 2019. 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-2019-11703 in the wild and no public exploit code.

Affected product: Mozilla Thunderbird. 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-2019-11703/ (Markdown: https://insights.sbomify.com/CVE-2019-11703/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-11703
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-11703
- OSV: https://osv.dev/vulnerability/CVE-2019-11703

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-11703/
Summaries are generated and may contain mistakes; the official description above is the record.