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CVE-2026-25833 Mbed TLS CVE debrief

CVE-2026-25833 is a HIGH severity vulnerability in Mbed TLS, a cryptographic library. The vulnerability is caused by a buffer overflow in the x509_inet_pton_ipv6() function. It affects Mbed TLS versions from 3.5.0 to 3.6.5 and 4.0.0. The vulnerability was published on [cvePublishedAt] and last modified on [cveModifiedAt].

Vendor
Mbed TLS
Product
Mbed TLS
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-01
Original CVE updated
2026-06-05
Advisory published
2026-04-01
Advisory updated
2026-06-05

Who should care

Users of Mbed TLS, especially those using versions 3.5.0 to 3.6.5 and 4.0.0, should be aware of this vulnerability and take steps to mitigate it.

Technical summary

The vulnerability is caused by a buffer overflow in the x509_inet_pton_ipv6() function in Mbed TLS. This function is used for parsing IPv6 addresses. The buffer overflow can be exploited remotely, allowing an attacker to potentially execute arbitrary code or cause a denial of service.

Defensive priority

HIGH

Recommended defensive actions

  • Upgrade to Mbed TLS version 3.6.6 or 4.1.0, which fixes the vulnerability.
  • Refer to [ref-4] and [ref-5] for vendor advisories and mitigation strategies.

Evidence notes

The vulnerability has a CVSS score of 7.5 and is classified as HIGH severity. The CVSS vector is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-25833 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-25833

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-25833 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-25833

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.