# CVE-2026-2968: Cesanta Mongoose Poly1305 Authentication Tag tls_chacha20.c mg_chacha20_poly1305_decrypt signature verification

> Remote attackers can bypass Poly1305 authentication tag verification in Cesanta Mongoose due to improper cryptographic signature checks.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 23 Feb 2026
- **Updated:** 23 Feb 2026
- **Also known as:** DEBIAN-CVE-2026-2968, GHSA-jprc-mg35-68jq, JLSEC-2026-368, UBUNTU-CVE-2026-2968

## What is CVE-2026-2968?

CVE-2026-2968 is a medium-severity vulnerability in Cesanta Mongoose, published on 23 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was detected in Cesanta Mongoose up to 7.20. This impacts the function mg_chacha20_poly1305_decrypt of the file /src/tls_chacha20.c of the component Poly1305 Authentication Tag Handler. The manipulation results in improper verification of cryptographic signature. The attack may be launched remotely. This attack is characterized by high complexity. The exploitability is said to be difficult. The exploit is now public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-345 (Insufficient Verification of Data Authenticity)

## Which versions are affected by CVE-2026-2968?

It affects 1 product.


Products: Cesanta Mongoose.

## How do I fix CVE-2026-2968?

No fix published yet.

## Is CVE-2026-2968 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-2968 exists.

## Other vulnerabilities in Cesanta Mongoose

- [CVE-2022-25299](https://insights.sbomify.com/CVE-2022-25299/): Arbitrary File Write (critical 9.8)
- [CVE-2020-25756](https://insights.sbomify.com/CVE-2020-25756/): Memory corruption in n/a (critical 9.8)
- [CVE-2019-19307](https://insights.sbomify.com/CVE-2019-19307/): Integer overflow in n/a (critical 9.8)
- [CVE-2019-12951](https://insights.sbomify.com/CVE-2019-12951/): Memory corruption in n/a (critical 9.8)
- [CVE-2018-20353](https://insights.sbomify.com/CVE-2018-20353/): Use after free in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-2968 and fix it if it is affected.

What it is: CVE-2026-2968 is a medium-severity vulnerability in Cesanta Mongoose, published on 23 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-2968 exists.

Affected product: Cesanta Mongoose. 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-2026-2968/ (Markdown: https://insights.sbomify.com/CVE-2026-2968/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-2968
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2968
- OSV: https://osv.dev/vulnerability/CVE-2026-2968

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-2968/
Summaries are generated and may contain mistakes; the official description above is the record.