# CVE-2026-77587: Use after free in Tor

> A malicious exit node can crash a Tor client by triggering a use-after-free in conflux object handling.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/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:** 20 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-77587, GHSA-9mf5-x83c-fg2x, UBUNTU-CVE-2026-77587

## What is CVE-2026-77587?

CVE-2026-77587 is a medium-severity use after free vulnerability in torproject Tor, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Tor before 0.4.9.11 is prone to a use-after-free (and potential double free) of a conflux object when a recovery leg revives a conflux set whose last linked leg has already been closed. A malicious exit node could use this to crash a client. This is TROVE-2026-026.

Weakness: CWE-416 (Use After Free), CWE-911 (Improper Update of Reference Count)

## Which versions are affected by CVE-2026-77587?

It affects 1 product.


Products: Torproject Tor.

## How do I fix CVE-2026-77587?

Upgrade to a fixed version.

## Is CVE-2026-77587 being exploited?

There is no known exploitation of CVE-2026-77587 in the wild and no public exploit code.

## Other vulnerabilities in torproject Tor

- [CVE-2026-77638](https://insights.sbomify.com/CVE-2026-77638/): Race condition in Tor (high 8.9)
- [CVE-2026-77642](https://insights.sbomify.com/CVE-2026-77642/): Memory corruption in Tor (high 7.5)
- [CVE-2022-33903](https://insights.sbomify.com/CVE-2022-33903/): Denial of service in n/a (high 7.5)
- [CVE-2021-38385](https://insights.sbomify.com/CVE-2021-38385/): Denial of service in n/a (high 7.5)
- [CVE-2021-34548](https://insights.sbomify.com/CVE-2021-34548/): Security feature bypass in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77587 and fix it if it is affected.

What it is: CVE-2026-77587 is a medium-severity use after free vulnerability in torproject Tor, published on 20 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-2026-77587 in the wild and no public exploit code.

Affected product: torproject Tor. 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-2026-77587/ (Markdown: https://insights.sbomify.com/CVE-2026-77587/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77587
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77587
- OSV: https://osv.dev/vulnerability/CVE-2026-77587

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77587/
Summaries are generated and may contain mistakes; the official description above is the record.