# CVE-2020-27743: Weak cryptography in n/a

> Failure to check random number generation in libtac allows predictable session IDs, potentially enabling authentication bypass.

- **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:** 26 Oct 2020
- **Updated:** 4 Aug 2024
- **Also known as:** UBUNTU-CVE-2020-27743

## What is CVE-2020-27743?

CVE-2020-27743 is a critical vulnerability in n/a, published on 26 Oct 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

libtac in pam_tacplus through 1.5.1 lacks a check for a failure of RAND_bytes()/RAND_pseudo_bytes(). This could lead to use of a non-random/predictable session_id.

Weakness: CWE-330 (Use of Insufficiently Random Values)

## Which versions are affected by CVE-2020-27743?

It affects 1 product.


Products: Pam Tacplus Project Pam Tacplus.

## How do I fix CVE-2020-27743?

No fix has been published for CVE-2020-27743 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-27743 being exploited?

There is no known exploitation of CVE-2020-27743 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2016-20014](https://insights.sbomify.com/CVE-2016-20014/): Information disclosure in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-27743 and fix it if it is affected.

What it is: CVE-2020-27743 is a critical vulnerability in n/a, published on 26 Oct 2020. 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-2020-27743 in the wild and no public exploit code.

Affected product: n/a. 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-2020-27743/ (Markdown: https://insights.sbomify.com/CVE-2020-27743/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-27743
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-27743
- OSV: https://osv.dev/vulnerability/CVE-2020-27743

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-27743/
Summaries are generated and may contain mistakes; the official description above is the record.