CVE-2026-45271

MediumCVSS 5.5

Published: 21/08/2026(UTC)Updated: 12/10/2026(UTC)Translated: 22/08/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.15%

4th percentile - higher than 4% of all known CVEs

Summary

Picotls is a TLS protocol library that allows users to select different crypto backends. Prior to commit c14231d801407640bc42c2dcf92783409ea6a7c7, the ASN.1 validator recursively descends into constructed ASN.1 elements without enforcing a maximum nesting depth. If an application loads an attacker-supplied private-key file through ptls_minicrypto_load_private_key(), or otherwise calls the public ASN.1 validation API on untrusted DER, a crafted deeply nested ASN.1 structure can exhaust the process stack and crash the application.

Risk Assessment

The risk is the potential for remote or local denial of service (application crash) by supplying a specially crafted private key file or DER data. The libcrypto (OpenSSL) backend is immune, but applications using the minicrypto backend are vulnerable.

Recommendation

It is recommended to immediately update the Picotls library to a version containing commit c14231d801407640bc42c2dcf92783409ea6a7c7. If not possible, avoid loading untrusted private key files and restrict access to the ASN.1 validation API.

Other vulnerabilities in Picotls

CVE-2026-59993Medium
Picotls is a TLS protocol library that allows users to select different crypto backends. In affected revisions through 44bc503, when picotls is used as a client-side TLS stack, a peer can send a HelloRetryRequest followed by a spoofed Hello message that causes a null-pointer dereference. This can terminate the consuming process, including a process performing other work, resulting in denial of service. This issue is fixed in commit a06ca41.

Original NVD description (English source)

Picotls is a TLS protocol library that allows users select different crypto backends based on their use case. Picotls implements its own ASN.1 validation helper, which is used by the minicrypto backend while parsing local PKCS#8 private keys. Prior to commit c14231d801407640bc42c2dcf92783409ea6a7c7, the validator recursively descends into constructed ASN.1 elements without enforcing a maximum nesting depth. If an application loads an attacker-supplied private-key file through ptls_minicrypto_load_private_key(), or otherwise calls the public ASN.1 validation API on untrusted DER, a crafted deeply nested ASN.1 structure can exhaust the process stack and crash the application. Note that the libcrypto (OpenSSL) backend does not use the ASN.1 validation helper of picotls, and therefore is immune to this vulnerability. The vulnerability has been addressed in commit c14231d801407640bc42c2dcf92783409ea6a7c7.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS