# CVE-2026-16028: Protocol::HTTP2 versions before 1.14 for Perl allow memory exhaustion via closed streams that stream_state never removes from the connection stream table.

> Attackers can exhaust server memory by repeatedly opening and closing HTTP/2 streams, causing denial of service in applications using the Protocol::HTTP2 Perl module.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-16028, GHSA-4hff-3256-7fpc, SUSE-SU-2026:23945-1, SUSE-SU-2026:4182-1, UBUNTU-CVE-2026-16028, openSUSE-SU-2026:11735-1, openSUSE-SU-2026:21972-1

## What is CVE-2026-16028?

CVE-2026-16028 is a high-severity denial of service vulnerability in perl-Protocol-HTTP2, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Protocol::HTTP2 versions before 1.14 for Perl allow memory exhaustion via closed streams that stream_state never removes from the connection stream table.

When a stream reaches the CLOSED state, stream_state returns the concurrency slot and clears most of the stream's keys, but the entry itself stays in the connection stream table and nothing in the distribution removes it. Stream identifiers increase monotonically, so a peer can open and close streams on one connection indefinitely, each close leaving a residual entry that is retained for the life of the connection.

SETTINGS_MAX_CONCURRENT_STREAMS does not bound this. That setting caps how many streams are live at once and is enforced, while the growth is made of streams the cap has already released, so it accumulates with concurrency never exceeding one. The client keeps the same table and grows the same way against a hostile server.

Measured against a server built on this module, roughly 920 bytes are retained per closed stream for about 19 bytes on the wire, so 100,000 sequential streams on one connection grow server resident memory by about 88 MiB. The streams are ordinary requests that the application accepts and completes.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-16028?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `perl-Protocol-HTTP2` | SUSE:Linux Enterprise Module for Package Hub 15 SP7 | All versions | 1.10-150600.3.6.1 |
| `perl-Protocol-HTTP2` | SUSE:Linux Enterprise Server 16.0 | All versions | 1.10-160000.4.1 |
| `perl-Protocol-HTTP2` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 1.10-160000.4.1 |
| `perl-Protocol-HTTP2` | openSUSE:Leap 16.0 | All versions | 1.10-160000.4.1 |
| `perl-Protocol-HTTP2` | openSUSE:Tumbleweed | All versions | 1.140.0-1.1 |

## How do I fix CVE-2026-16028?

Upgrade to a fixed version.

## Is CVE-2026-16028 being exploited?

There is no known exploitation of CVE-2026-16028 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-16028 and fix it if it is affected.

What it is: CVE-2026-16028 is a high-severity denial of service vulnerability in perl-Protocol-HTTP2, published on 7 Sep 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-2026-16028 in the wild and no public exploit code.

Affected product: perl-Protocol-HTTP2. 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-2026-16028/ (Markdown: https://insights.sbomify.com/CVE-2026-16028/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-16028
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16028
- OSV: https://osv.dev/vulnerability/CVE-2026-16028

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-16028/
Summaries are generated and may contain mistakes; the official description above is the record.