# CVE-2019-1010083: Pallets Project Flask is vulnerable to Denial of Service via Unexpected memory usage

> Attackers can cause denial of service in Flask applications by sending crafted encoded JSON data, leading to unexpected memory usage.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 17 Jul 2019
- **Updated:** 5 Aug 2024
- **Also known as:** CLSA-2026-1772323849, DEBIAN-CVE-2019-1010083, GHSA-5wv5-4vpf-pj6m, PYSEC-2019-179, SUSE-SU-2023:1928-1

## What is CVE-2019-1010083?

CVE-2019-1010083 is a high-severity denial of service vulnerability in The Pallets Project Flask, published on 17 Jul 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The Pallets Project Flask before 1.0 is affected by: unexpected memory usage. The impact is: denial of service. The attack vector is: crafted encoded JSON data. The fixed version is: 1. NOTE: this may overlap CVE-2018-1000656.

## Which versions are affected by CVE-2019-1010083?

3 open source packages ship an affected version, including flask and Flask. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `flask` | PyPI | All versions | 1.0 |
| `flask` | PyPI | All versions | 1.0 |
| `Flask` | PyPI | All versions | 1.0 |
| `python-Flask` | SUSE:Linux Enterprise Module for Public Cloud 12 | All versions | 0.12.1-7.7.1 |

Products: Palletsprojects Flask.

## How do I fix CVE-2019-1010083?

Upgrade flask to 1.0 or later.

## Is CVE-2019-1010083 being exploited?

There is no known exploitation of CVE-2019-1010083 in the wild and no public exploit code.

## Other vulnerabilities in The Pallets Project Flask

- [CVE-2023-30861](https://insights.sbomify.com/CVE-2023-30861/): Flask vulnerable to possible disclosure of permanent session cookie due to missing Vary: Cookie header (high 7.5)
- [CVE-2026-27205](https://insights.sbomify.com/CVE-2026-27205/): Flask session does not add `Vary: Cookie` header when accessed in some ways (low 2.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-1010083 and fix it if it is affected.

What it is: CVE-2019-1010083 is a high-severity denial of service vulnerability in The Pallets Project Flask, published on 17 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-2019-1010083 in the wild and no public exploit code.

Affected packages and fixed versions:
- flask (PyPI): affected all versions; fixed in 1.0
- flask (PyPI): affected all versions; fixed in 1.0
- Flask (PyPI): affected all versions; fixed in 1.0

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-2019-1010083/ (Markdown: https://insights.sbomify.com/CVE-2019-1010083/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-1010083
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-1010083
- OSV: https://osv.dev/vulnerability/CVE-2019-1010083

---
From sbomify Insights: https://insights.sbomify.com/CVE-2019-1010083/
Summaries are generated and may contain mistakes; the official description above is the record.