# CVE-2026-12707: Unbounded path event queue growth in quiche via peer-driven source connection ID rotation

> A remote attacker can cause memory exhaustion in Cloudflare quiche by triggering unbounded path event queue growth via rapid connection migration.

- **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:** No
- **Published:** 14 Jul 2026
- **Updated:** 14 Jul 2026
- **Also known as:** GHSA-4q5x-gp38-rfp4

## What is CVE-2026-12707?

CVE-2026-12707 is a high-severity denial of service vulnerability in Cloudflare quiche, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Summary

Cloudflare quiche was discovered to be vulnerable to memory resource exhaustion due to unbounded queuing of post-handshake client migration events.

Impact

quiche supports the connection migration features described in Section 9 of RFC 9000, which allows a single QUIC connection to survive changes in the network path. Although quiche implements the protections described in Section 9.3 of RFC 9000 to limit server state commitment, it was discovered that the collection of PathEvents, intended to be consumed by applications via the path_event_next() function, was not bounded.

Once the QUIC handshake completed, a peer could exploit rapid source address migration in order to cause unbounded queuing of the PathEvent::ReusedSourceConnectionId type. Servers are vulnerable even if active connection migration is disabled.

Mitigation:

  *  

Applications can call path_event_next() to drain the PathEvent collection, mitigating the attack.

  *  

Users are requested to upgrade to quiche 0.29.3 which is the earliest version that prevents excessive queueing of PathEvent::ReusedSourceConnectionId.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-12707?


## How do I fix CVE-2026-12707?

No fix has been published for CVE-2026-12707 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-12707 being exploited?

There is no known exploitation of CVE-2026-12707 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12707 and fix it if it is affected.

What it is: CVE-2026-12707 is a high-severity denial of service vulnerability in Cloudflare quiche, published on 14 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-2026-12707 in the wild and no public exploit code.

Affected product: Cloudflare quiche. 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-2026-12707/ (Markdown: https://insights.sbomify.com/CVE-2026-12707/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12707
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12707
- OSV: https://osv.dev/vulnerability/CVE-2026-12707

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-12707/
Summaries are generated and may contain mistakes; the official description above is the record.