In Tor before 0.3.3.12, 0.3.4.x before 0.3.4.11, 0.3.5.x before 0.3.5.8, and 0.4.x before 0.4.0.2-alpha, remote denial of service against To
In Tor before 0.3.3.12, 0.3.4.x before 0.3.4.11, 0.3.5.x before 0.3.5.8, and 0.4.x before 0.4.0.2-alpha, remote denial of service against Tor clients and relays can occur via memory exhaustion in the KIST cell scheduler.
- Published
- Feb 21, 2019
- Updated
- Jun 16, 2026
- EPSS
- 4.6% · 91th percentile
- CWE
- CWE-770
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Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 4.6%
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| torproject | tor | cpe:2.3:a:torproject:tor |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- torproject torbefore 0.3.3.12
- torproject tor0.3.4.8 and later · before 0.3.4.11
- torproject tor0.3.4.0
- torproject tor0.3.4.1
- torproject tor0.3.4.2
- torproject tor0.3.4.3
- torproject tor0.3.4.4
- torproject tor0.3.4.5
- torproject tor0.3.4.6
- torproject tor0.3.4.7
- torproject tor0.3.5.0
- torproject tor0.3.5.1
- torproject tor0.3.5.2
- torproject tor0.3.5.3
- torproject tor0.3.5.4
- torproject tor0.3.5.5
- torproject tor0.3.5.6
- torproject tor0.3.5.7
- torproject tor0.4.0.1
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | tor | before 0.3.5.8-1 | 0.3.5.8-1 |
| openSUSE:Tumbleweed | tor | before 0.4.6.7-2.2 | 0.4.6.7-2.2 |
| SUSE:Package Hub 12 | tor | before 0.3.4.11-bp150.3.6.1 | 0.3.4.11-bp150.3.6.1 |
| SUSE:Package Hub 12 | tor | before 0.3.4.11-bp150.3.6.1 | 0.3.4.11-bp150.3.6.1 |
Same product
torproject: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-77642tor before 0.4.9.9 was prone to an out-of-bounds write when parsing a consensus or detached signature with unexpected signature digest type37Monitor
- CVE-2026-77638Tor before 0.4.9.11 is prone to a race condition where in just the right circumstances a rendezvous point could man-in-the-middle (impersona36Monitor
- CVE-2026-44603Tor before 0.4.9.7 has an out-of-bounds read by one byte via a malformed BEGIN cell, aka TROVE-2026-007.36Monitor
- CVE-2026-44597Tor before 0.4.9.7 has an out-of-bounds read when an END, a TRUNCATE, or a TRUNCATED cell lacks a reason in its payload, aka TROVE-2026-011.36Monitor
- CVE-2018-0491A use-after-free issue was discovered in Tor 0.3.2.x before 0.3.2.10.34Monitor
- CVE-2026-77641tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails.32Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:tor | 0.3.5.8-1 · Debian:12 | Package registry (OSV) |
| opensuse:tor | 0.3.4.11-bp150.3.6.1 · openSUSE:Leap 15.0 | Package registry (OSV) |
| suse:tor | 0.3.4.11-bp150.3.6.1 · SUSE:Package Hub 12 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-770 · Allocation of Resources Without Limits or ThrottlingCVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- FloodingCAPEC-125likelihood: High · Medium
- Excessive AllocationCAPEC-130likelihood: Medium · Medium
- XML Ping of the DeathCAPEC-147likelihood: Low · Medium
- Exponential Data ExpansionCAPEC-197likelihood: High · Medium
- Serialized Data Parameter BlowupCAPEC-229likelihood: High · High
- Serialized Data with Nested PayloadsCAPEC-230likelihood: Medium · High
- Oversized Serialized Data PayloadsCAPEC-231likelihood: Medium · High
- HTTP DoSCAPEC-469Low
ATT&CK techniques
- Network Denial of Service:Direct Network FloodT1498.001
- Network Denial of Service:Reflection AmplificationT1498.002
- Endpoint Denial of ServiceT1499
- Endpoint Denial of Service: OS Exhaustion FloodT1499.001
- Endpoint Denial of Service:Service Exhaustion FloodT1499.002
- Endpoint Denial of Service:Application Exhaustion FloodT1499.003
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- lists.opensuse.org/opensuse-security-announce/2019-04/msg00013.html
- www.securityfocus.com/bid/107136
- blog.torproject.org/new-releases-tor-0402-alpha-0358-03411-and-03312
- trac.torproject.org/projects/tor/ticket/29168
Vendor advisories and official records. Exploit/PoC links are deliberately left out.