# CVE-2021-1104: Information disclosure in Machine Trap Base Address (MTVEC) Register

> Undefined initial state of the MTVEC register in RISC-V processors may allow attackers to disclose information, tamper with data, or cause denial of service.

- **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:** No
- **Published:** 13 Aug 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-5pxp-m22f-2m9x

## What is CVE-2021-1104?

CVE-2021-1104 is a critical vulnerability in RISCV.org Machine Trap Base Address (MTVEC) Register, published on 13 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The RISC-V Instruction Set Manual contains a documented ambiguity for the Machine Trap Vector Base Address (MTVEC) register that may lead to a vulnerability due to the initial state of the register not being defined, potentially leading to information disclosure, data tampering and denial of service.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2021-1104?

It affects 1 product.


Products: Risc-v Instruction Set Manual.

## How do I fix CVE-2021-1104?

No fix has been published for CVE-2021-1104 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-1104 being exploited?

There is no known exploitation of CVE-2021-1104 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-1104 and fix it if it is affected.

What it is: CVE-2021-1104 is a critical vulnerability in RISCV.org Machine Trap Base Address (MTVEC) Register, published on 13 Aug 2021. 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-2021-1104 in the wild and no public exploit code.

Affected product: RISCV.org Machine Trap Base Address (MTVEC) Register. 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-2021-1104/ (Markdown: https://insights.sbomify.com/CVE-2021-1104/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-1104
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-1104
- OSV: https://osv.dev/vulnerability/CVE-2021-1104

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-1104/
Summaries are generated and may contain mistakes; the official description above is the record.