ARM mbed TLS before 1.3.21 and 2.x before 2.1.9, if optional authentication is configured, allows remote attackers to bypass peer authentica
ARM mbed TLS before 1.3.21 and 2.x before 2.1.9, if optional authentication is configured, allows remote attackers to bypass peer authentication via an X.509 certificate chain with many intermediates. NOTE: although mbed TLS was formerly known as PolarSSL, the releases shipped with the PolarSSL name are not affected.
- Published
- Aug 30, 2017
- Updated
- Jun 16, 2026
- EPSS
- 1.5% · 73th percentile
- CWE
- CWE-287
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Report tools
Action score
32
Monitor
Low priority for now.
- CVSS
- 32 / 40 · 8.1 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 1.5%
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| arm | mbed tls | cpe:2.3:a:arm:mbed_tls |
| trustedfirmware | mbed tls | cpe:2.3:a:trustedfirmware:mbed_tls |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- arm mbed tls1.3.19
- arm mbed tls1.3.21
- arm mbed tls2.1.7
- arm mbed tls2.1.9
- arm mbed tls2.4.2
- arm mbed tls2.6.2
- trustedfirmware mbed tls1.3.10
- trustedfirmware mbed tls1.3.11
- trustedfirmware mbed tls1.3.12
- trustedfirmware mbed tls1.3.13
- trustedfirmware mbed tls1.3.14
- trustedfirmware mbed tls1.3.15
- trustedfirmware mbed tls1.3.16
- trustedfirmware mbed tls1.3.17
- trustedfirmware mbed tls1.3.18
- trustedfirmware mbed tls1.3.20
- trustedfirmware mbed tls2.0.0
- trustedfirmware mbed tls2.1.0
- trustedfirmware mbed tls2.1.1
- trustedfirmware mbed tls2.1.2
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.10 | mbedtls | before 2.6.0-r0 | 2.6.0-r0 |
| Debian:12 | mbedtls | before 2.6.0-1 | 2.6.0-1 |
| Debian:9 | mbedtls | before 2.4.2-1+deb9u1 | 2.4.2-1+deb9u1 |
| openSUSE:Tumbleweed | mbedtls-2 | before 2.27.0-1.2 | 2.27.0-1.2 |
| openSUSE:Tumbleweed | mbedtls-3 | before 3.6.6-1.1 | 3.6.6-1.1 |
| SUSE:Package Hub 12 | mbedtls | before 1.3.19-8.1 | 1.3.19-8.1 |
Same product
arm: all recordsOther highest-scoring records for the same primary product.
- CVE-2025-47917Mbed TLS before 3.6.4 allows a use-after-free in certain situations of applications that are developed in accordance with the documentation.40Plan
- CVE-2021-44732Mbed TLS before 3.0.1 has a double free in certain out-of-memory conditions, as demonstrated by an mbedtls_ssl_set_session() failure.40Plan
- CVE-2017-18187In ARM mbed TLS before 2.7.0, there is a bounds-check bypass through an integer overflow in PSK identity parsing in the ssl_parse_client_psk40Plan
- CVE-2018-0488ARM mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0, when the truncated HMAC extension and CBC are used, allows remote attackers to 40Plan
- CVE-2018-0487ARM mbed TLS before 1.3.22, before 2.1.10, and before 2.7.0 allows remote attackers to execute arbitrary code or cause a denial of service (40Plan
- CVE-2026-34877An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0.39Monitor
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 |
|---|---|---|
| alpine:mbedtls | 2.6.0-r0 · Alpine:v3.10 | Package registry (OSV) |
| debian:mbedtls | 2.6.0-1 · Debian:12 | Package registry (OSV) |
| opensuse:mbedtls-2 | 2.27.0-1.2 · openSUSE:Tumbleweed | Package registry (OSV) |
| opensuse:mbedtls-3 | 3.6.6-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| suse:mbedtls | 1.3.19-8.1 · 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.
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.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-287 · Improper AuthenticationCVSS vector
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
nvd-primary
Root cause
Authentication is added route by route instead of being enforced in one place. When a route added later bypasses the shared middleware, the session check never runs for it.
The bug in code
The whole CWE-287 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
app.use("/admin", requireSession, adminRouter);
// Route added later skips the middlewareapp.post("/admin-api/config", updateConfig);Fixed
const admin = express.Router();admin.use(requireSession, requireRole("admin"));
admin.post("/config", updateConfig);app.use("/admin", admin);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)
- Authentication AbuseCAPEC-114Medium
- Authentication BypassCAPEC-115Medium
- Identity SpoofingCAPEC-151likelihood: Medium · Medium
- Fake the Source of DataCAPEC-194Medium
- Exploiting Trust in ClientCAPEC-22likelihood: High · High
- Utilizing REST's Trust in the System Resource to Obtain Sensitive DataCAPEC-57likelihood: Medium · Very High
- Session HijackingCAPEC-593likelihood: High · Very High
- Token ImpersonationCAPEC-633Medium
ATT&CK techniques
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/2017/dsa-3967
- bugs.debian.org/873557
- github.com/ARMmbed/mbedtls/commit/31458a18788b0cf0b722acda9bb2f2fe13a3fb32
- github.com/ARMmbed/mbedtls/commit/d15795acd5074e0b44e71f7ede8bdfe1b48591fc
- tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2017-02
Vendor advisories and official records. Exploit/PoC links are deliberately left out.