# CVE-2026-49457: QUIC has Broken TLS verification

> A man-in-the-middle can impersonate servers because the Erlang QUIC client failed to validate TLS certificates, compromising connection confidentiality and integrity.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Aug 2026
- **Updated:** 14 Aug 2026
- **Also known as:** GHSA-2r8v-p65x-3663

## What is CVE-2026-49457?

CVE-2026-49457 is a critical vulnerability in benoitc erlang_quic, published on 14 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

erlang_quic is a pure Erlang QUIC implementation. Prior to version 1.4.4, the QUIC client did not authenticate the server during the TLS 1.3 handshake. The CertificateVerify signature was not checked, the certificate chain was not validated, and the hostname was not compared against the certificate, so `verify` was effectively a no-op on the client. A man-in-the-middle on the network path could present any certificate and impersonate any server, defeating the confidentiality and integrity of the connection. HTTP/3 uses the same client and was equally affected. Handshakes authenticated by a PSK (session resumption) are not affected, because the peer is authenticated by the PSK binder and no certificate is sent. This is fixed in 1.4.4. The client now verifies the CertificateVerify signature, validates the certificate chain against the trust store (`cacerts` option, the operating system store by default), and checks the hostname. Client `verify` now defaults to on; set `verify => false` to accept any certificate (for example a self-signed test server). No known workarounds are available before 1.4.4. `verify => true` had no effect, and inspecting the certificate after connecting does not help because without the signature check the peer is never proven to own the certificate it presents.

Weakness: CWE-297 (Improper Validation of Certificate with Host Mismatch), CWE-295 (Improper Certificate Validation)

## Which versions are affected by CVE-2026-49457?

2 open source packages ship an affected version, including quic.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `quic` | Hex | All versions | 1.4.4 |
| `quic` | Hex | All versions | 1.4.4 |

## How do I fix CVE-2026-49457?

Upgrade quic to 1.4.4 or later.

## Is CVE-2026-49457 being exploited?

There is no known exploitation of CVE-2026-49457 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49457 and fix it if it is affected.

What it is: CVE-2026-49457 is a critical vulnerability in benoitc erlang_quic, published on 14 Aug 2026. 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-2026-49457 in the wild and no public exploit code.

Affected packages and fixed versions:
- quic (Hex): affected all versions; fixed in 1.4.4
- quic (Hex): affected all versions; fixed in 1.4.4

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-2026-49457/ (Markdown: https://insights.sbomify.com/CVE-2026-49457/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49457
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49457
- OSV: https://osv.dev/vulnerability/CVE-2026-49457

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49457/
Summaries are generated and may contain mistakes; the official description above is the record.