How severe is CVE-2026-34873?

CVE-2026-34873 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-34873 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34873?

CVE-2026-34873 affects Trustedfirmware Mbed Tls. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34873?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-34873 have an EU (EUVD) identifier?

Yes. CVE-2026-34873 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18064.

When was CVE-2026-34873 published?

CVE-2026-34873 was published on 2026-04-01 and last updated on 2026-06-17.

CVE-2026-34873

CVE-2026-34873 is a critical-severity vulnerability in Trustedfirmware Mbed Tls with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-287.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 0% (16th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18064
Weakness: CWE-287
Affected product: Trustedfirmware Mbed Tls
Published: 2026-04-01
Last modified: 2026-06-17

Description

An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.

Frequently asked questions

What is CVE-2026-34873?: An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.
How severe is CVE-2026-34873?: CVE-2026-34873 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-34873 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34873?: CVE-2026-34873 affects Trustedfirmware Mbed Tls. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34873?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-34873 have an EU (EUVD) identifier?: Yes. CVE-2026-34873 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18064.
When was CVE-2026-34873 published?: CVE-2026-34873 was published on 2026-04-01 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:trustedfirmware:mbed_tls:*:*:*:*:*:*:*:*

More vulnerabilities in Trustedfirmware Mbed Tls

CVE-2026-34877 — Critical (CVSS 9.8): An issue was discovered in Mbed TLS versions from 2.19.0 up to 3.6.5, Mbed TLS 4.0.0. Insufficient protection of…
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CVE-2024-45158 — Critical (CVSS 9.8): An issue was discovered in Mbed TLS 3.6 before 3.6.1. A stack buffer overflow in mbedtls_ecdsa_der_to_raw() and…
CVE-2023-45199 — Critical (CVSS 9.8): Mbed TLS 3.2.x through 3.4.x before 3.5 has a Buffer Overflow that can lead to remote Code execution.

All CVEs affecting Trustedfirmware Mbed Tls →

Other CWE-287 (Improper Authentication) vulnerabilities

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CVE-2026-56162 — Critical (CVSS 10.0): Improper authentication in Azure SQL Database allows an unauthorized attacker to elevate privileges over a network.
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Browse all CWE-287 (Improper Authentication) vulnerabilities →