CVE-2026-45271

Received Received - Intake

Stack Overflow in Picotls ASN.1 Parser

Publication date: 2026-08-21

Last updated on: 2026-08-21

Assigner: GitHub, Inc.

Description

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.

CVSS Scores

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Meta Information

Published

2026-08-21

Last Modified

2026-08-21

Generated

2026-08-22

AI Q&A

2026-08-22

EPSS Evaluated

N/A

NVD

CVE-2026-45271

Affected Vendors & Products

Vendor	Product	Version / Range
picotls	picotls	to c14231d801407640bc42c2dcf92783409ea6a7c7 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-835	The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

Attack-Flow Graph

Executive Summary

Picotls is a TLS library that allows custom crypto backends. It has a flaw in its ASN.1 validation helper used by the minicrypto backend when parsing PKCS#8 private keys. The issue is that it does not limit how deep ASN.1 structures can be nested, allowing deeply nested malicious structures to crash the application by exhausting the stack.

Detection Guidance

This vulnerability can be detected by checking if your system uses the vulnerable version of Picotls with the minicrypto backend. Inspect the Picotls version and backend in use. No specific commands are provided in the context to detect exploitation attempts.

Impact Analysis

If you use the minicrypto backend in Picotls and load a crafted private key file or process untrusted DER data, an attacker could crash your application by causing a stack overflow. This could lead to denial of service or potential code execution if combined with other exploits.

Mitigation Strategies

Update Picotls to the patched commit c14231d801407640bc42c2dcf92783409ea6a7c7 or later. If using the minicrypto backend, ensure no untrusted DER inputs are processed. Avoid loading attacker-supplied private keys via ptls_minicrypto_load_private_key().

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