Stunnel 5.00 through 5.13, when using the redirect option, does not redirect client connections to the expected server after the initial con
Stunnel 5.00 through 5.13, when using the redirect option, does not redirect client connections to the expected server after the initial connection, which allows remote attackers to bypass authentication.
- Published
- May 13, 2015
- Updated
- Jun 16, 2026
- EPSS
- 2.1% · 81th percentile
- CWE
- CWE-284
Sign in to follow · You’ll be notified if a followed record enters KEV, gets an exploit or is updated.
Report tools
Action score
24
Monitor
Low priority for now.
- CVSS
- 23 / 40 · 5.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 2.1%
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| stunnel | stunnel | cpe:2.3:a:stunnel:stunnel |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- stunnel stunnel5.00
- stunnel stunnel5.01
- stunnel stunnel5.02
- stunnel stunnel5.03
- stunnel stunnel5.04
- stunnel stunnel5.05
- stunnel stunnel5.06
- stunnel stunnel5.07
- stunnel stunnel5.08
- stunnel stunnel5.09
- stunnel stunnel5.10
- stunnel stunnel5.11
- stunnel stunnel5.12
- stunnel stunnel5.13
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | stunnel4 | before 3:5.18-1 | 3:5.18-1 |
| Debian:8 | stunnel4 | before 3:5.06-2+deb8u1 | 3:5.06-2+deb8u1 |
| openSUSE:Tumbleweed | stunnel | before 5.65-1.1 | 5.65-1.1 |
| SUSE:Linux Enterprise Server 12 | stunnel | before 5.00-3.1 | 5.00-3.1 |
Same product
stunnel: all recordsOther highest-scoring records for the same primary product.
- CVE-2001-0060Format string vulnerability in stunnel 3.8 and earlier allows attackers to execute arbitrary commands via a malformed ident username.41Plan
- CVE-2011-2940stunnel 4.40 and 4.41 might allow remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via unspe39Monitor
- CVE-2002-0002Format string vulnerability in stunnel before 3.22 when used in client mode for (1) smtp, (2) pop, or (3) nntp allows remote malicious serve32Monitor
- CVE-2021-20230A flaw was found in stunnel before 5.57, where it improperly validates client certificates when it is configured to use both redirect and ve30Monitor
- CVE-2008-2400Unspecified vulnerability in stunnel before 4.23, when running as a service on Windows, allows local users to gain privileges via unknown at28Monitor
- CVE-2013-1762stunnel 4.21 through 4.54, when CONNECT protocol negotiation and NTLM authentication are enabled, does not correctly perform integer convers27Monitor
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:stunnel4 | 3:5.18-1 · Debian:12 | Package registry (OSV) |
| openSUSE:stunnel | 5.65-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| SUSE:stunnel | 5.00-3.1 · SUSE:Linux Enterprise Server 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
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
If successful
- Confidentiality
- P · data can be read
- Integrity
- P · data or configuration can be modified
- Availability
- none
- Attack complexity
- M
- Confidentiality impact
- P
- Integrity impact
- P
- Availability impact
- None
Weakness class (CWE)
CWE-284 · Improper Access ControlCVSS vector
AV:N/AC:M/Au:N/C:P/I:P/A:N
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)
- Embedding Scripts within ScriptsCAPEC-19likelihood: High · High
- Malicious Logic InsertionCAPEC-441likelihood: Medium · High
- Modification of Windows Service ConfigurationCAPEC-478likelihood: Low · High
- Malicious Root CertificateCAPEC-479likelihood: Low · Low
- Intent SpoofCAPEC-502
- WebView ExposureCAPEC-503
- Data Injected During ConfigurationCAPEC-536likelihood: Low · High
- Incomplete Data Deletion in a Multi-Tenant EnvironmentCAPEC-546likelihood: Low · Medium
ATT&CK techniques
- RootkitT1014
- Obfuscated Files or Information: Embedded PayloadsT1027.009
- Boot or Logon Initialization ScriptsT1037
- Taint shared contentT1080
- Server Software Component: Terminal Services DLLT1505.005
- Pre-OS Boot:BootkitT1542.003
- Create or Modify System ProcessT1543
- Create or Modify System Process: Launch AgentT1543.001
- Create or Modify System Process:Windows ServiceT1543.003
- Create or Modify System Process: Launch DaemonT1543.004
- Event Triggered Execution:Change Default File AssociationT1546.001
- Event Triggered Execution:.bash_profile and .bashrcT1546.004
- Event Triggered Execution: Accessibility FeaturesT1546.008
- Event Triggered Execution: Installer PackagesT1546.016
- Boot or Logon Autostart ExecutionT1547
- Boot or Logon Autostart Execution:Kernel Modules and ExtensionsT1547.006
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
- www.debian.org/security/2015/dsa-3299
- www.securityfocus.com/bid/74659
- www.securitytracker.com/id/1032324
- www.stunnel.org/CVE-2015-3644.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.