CVE-2026-77584: torproject tor Incorrect Synchronization
Vulnerability summary
CVE-2026-77584 is a high (CVSS 8.2) Incorrect Synchronization vulnerability in torproject tor. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.2% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 3 · Related 2Timeline
- 20-08-2026PublishedVulnerability first disclosed.
- 25-08-2026Last modifiedVulnerability information updated.
Description
Tor before 0.4.9.10 did not reject a CONFLUX_LINK cell that arrives on a circuit which already has attached streams. A malicious client could send a RELAY_COMMAND_BEGIN before the CONFLUX_LINK on the same circuit, attaching an exit stream that would later end up orphan leaving a dangling circuit back-pointer and a use-after-free (UAF) when the circuit is freed. This is TROVE-2026-025.
CVSS metrics
4 scores · 4 sources · 1 version- CVE.orgCNA7.0HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:LDiffers
- OSV · UbuntuEcosystem advisory · calculated8.2HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
- OSV · DebianEcosystem advisory · calculated8.2HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
EPSS trend
Probability
0.25%
Chance of exploitation in the next 30 days
Percentile
15%
Versus all other CVEs
30-day change
+0.07 pp
From 0.18% on 19-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian1 product
- tor< 0.4.9.11-0+deb12u1 | < 0.4.9.11-0+deb13u1 | < 0.4.9.11-1
Torproject1 product
- tor≥ 0.4.8.1-alpha, < 0.4.9.10 | < 0.4.9.10
Ubuntu1 product
- torAll versions (No fix recorded)
3 vendors · 3 products
