# CVE-2026-54891: Plaintext APPLICATION_DATA injected during TLS handshake delivered to client application post-handshake in ssl

> A network attacker can inject unauthenticated plaintext into TLS client connections, causing the application to process it as authenticated data.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Jul 2026
- **Updated:** 8 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-54891, EEF-CVE-2026-54891, GHSA-gf6r-99xw-6qg6, UBUNTU-CVE-2026-54891

## What is CVE-2026-54891?

CVE-2026-54891 is a medium-severity vulnerability in Erlang OTP, published on 2 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper Enforcement of Message Integrity During Transmission in a Communication Channel vulnerability in Erlang/OTP ssl (tls_gen_connection module) allows a network-positioned attacker to inject unauthenticated plaintext that the TLS client application later treats as authenticated server data.

The function tls_gen_connection:handle_protocol_record/3 rejects APPLICATION_DATA records that arrive in pre-handshake states when the TLS endpoint acts as a server, but does not apply the same check when the endpoint acts as a client. A network-positioned attacker can send plaintext APPLICATION_DATA records to the client during the handshake. The records are buffered and, once the handshake completes successfully, delivered to the application as if they were authenticated post-handshake data. The attacker cannot observe the client's response or steer the connection, so the impact is limited to blind injection of unauthenticated bytes. The injection window is wider for TLS versions prior to TLS 1.3 than for TLS 1.3.

This vulnerability is associated with program file lib/ssl/src/tls_gen_connection.erl.

TLS 1.3 is affected starting with OTP 22.0, when TLS 1.3 support was added.

This issue affects OTP from OTP 17.0 before OTP 27.3.4.14, from OTP 28.0 before OTP 28.5.0.3, and from OTP 29.0 before OTP 29.0.3, corresponding to ssl from 5.3.4 before 11.2.12.10, from 11.3 before 11.6.0.3, and from 11.7 before 11.7.3. Whether OTP before OTP 17.0, corresponding to ssl before 5.3.4, is affected is unknown.

Weakness: CWE-924 (Improper Enforcement of Message Integrity During Transmission in a Communication Channel)

## Which versions are affected by CVE-2026-54891?

It affects 2 products.


Products: Erlang Erlang\/Otp, Erlang Erlang\/Ssl.

## How do I fix CVE-2026-54891?

Upgrade to a fixed version.

## Is CVE-2026-54891 being exploited?

There is no known exploitation of CVE-2026-54891 in the wild and no public exploit code.

## Other vulnerabilities in Erlang OTP

- [CVE-2022-37026](https://insights.sbomify.com/CVE-2022-37026/): Auth bypass in n/a (critical 9.8)
- [CVE-2016-10253](https://insights.sbomify.com/CVE-2016-10253/): Memory corruption in n/a (critical 9.8)
- [CVE-2026-55953](https://insights.sbomify.com/CVE-2026-55953/): TLS 1.2 and DTLS client accepts unoffered anonymous cipher suite, bypassing server authentication (critical 9.1)
- [CVE-2026-49759](https://insights.sbomify.com/CVE-2026-49759/): Stack buffer overflow in SCTP error cause parsing in inet_drv allows remote VM crash (high 8.8)
- [CVE-2026-58227](https://insights.sbomify.com/CVE-2026-58227/): TLS/DTLS denial of service via unbounded recursion on cross-signed peer certificate chain (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54891 and fix it if it is affected.

What it is: CVE-2026-54891 is a medium-severity vulnerability in Erlang OTP, published on 2 Jul 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-2026-54891 in the wild and no public exploit code.

Affected product: Erlang OTP. 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-2026-54891/ (Markdown: https://insights.sbomify.com/CVE-2026-54891/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54891
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54891
- OSV: https://osv.dev/vulnerability/CVE-2026-54891

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54891/
Summaries are generated and may contain mistakes; the official description above is the record.