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Buffer underflow in x509_inet_pton_ipv6() (CVE-2026-25833) #435

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Bug
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Buffer underflow in x509_inet_pton_ipv6() (CVE-2026-25833)#435
Bug
Assignees
michaelthomasj
Labels
applies-to-v5.3.0applies-to-v5.4.0applies-to-v5.5.0applies-to-v5.6.0applies-to-v5.7.0applies-to-v5.8.0applies-to-v5.9.0applies-to-v6.0.0applies-to-v6.1.0applies-to-v6.2.0applies-to-v6.3.0product_security_advisory
Milestone
v6.5.0
@michaelthomasj

Description

@michaelthomasj
michaelthomasj
opened on May 6, 2026

Issue

A limited buffer underflow exists in x509_inet_pton_ipv6() when parsing IPv6 addresses in X.509 certificates and related inputs. In rare cases — for example on platforms with memory protection where the over-read crosses a page boundary — this can lead to a denial of service. Affects Mbed TLS 3.5.0 through 3.6.5.
https://nvd.nist.gov/vuln/detail/CVE-2026-25833

Workaround

Update to mbedTLS v3.6.6, TF-PSA-Crypto 1.1.0, or a newer version of either.
FSP v6.5.0 (scheduled for 2026/05/27) includes mbedTLS v3.6.6.

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