Quick answers
- Is CVE-2026-77584 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-77584 being exploited in the wild.
- How severe is CVE-2026-77584?
- High severity, with a CVSS score of 7, published 20 August 2026.
- Which products and versions are affected?
- Tor Project Tor before 0.4.9.10.
- Is there a fix for CVE-2026-77584?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-77584 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-77584?
- Check whether you run Torproject Tor. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is a use-after-free (UAF) flaw in Tor's circuit management code. The root cause is that Tor does not properly reject CONFLUX_LINK cells arriving on circuits that already have attached streams. An attacker can send a RELAY_COMMAND_BEGIN message before CONFLUX_LINK on the same circuit, creating an orphan exit stream with a dangling circuit back-pointer. When the circuit is subsequently freed, the dangling pointer causes a use-after-free condition, potentially leading to memory corruption or crashes. The attack is network-accessible and requires no prior authentication. Tor versions before 0.4.9.10 are affected; users should upgrade immediately.
Affected products
- Tor Project Tor before 0.4.9.10
Timeline
- 2026-08-20: disclosed