CVE-2026-45271
picotls has infinite recursion in the minicrypto ASN.1 decoder
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.
INFO
Published Date :
Aug. 21, 2026, 9:16 p.m.
Last Modified :
Oct. 12, 2026, 4:10 p.m.
Remotely Exploit :
No
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE |
Solution
- Update Picotls library to version c14231d801407640bc42c2dcf92783409ea6a7c7.
- Avoid parsing untrusted DER files with the ASN.1 validation API.
- Use the libcrypto backend if available.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-45271.
| URL | Resource |
|---|---|
| https://github.com/h2o/picotls/commit/c14231d801407640bc42c2dcf92783409ea6a7c7 | |
| https://github.com/h2o/picotls/security/advisories/GHSA-84f5-m5x2-82q4 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-45271 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-45271
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-45271 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-45271 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 12, 2026
Action Type Old Value New Value Added Translation Title: picotls de h2o, Description: Picotls es una biblioteca de protocolo TLS que permite a los usuarios seleccionar diferentes backends criptográficos según su caso de uso. Picotls implementa su propio asistente de validación ASN.1, que es utilizado por el backend minicrypto al analizar claves privadas PKCS#8 locales. Antes del commit c14231d801407640bc42c2dcf92783409ea6a7c7, el validador desciende recursivamente en elementos ASN.1 construidos sin imponer una profundidad máxima de anidamiento. Si una aplicación carga un archivo de clave privada suministrado por un atacante a través de ptls_minicrypto_load_private_key(), o de otro modo llama a la API pública de validación ASN.1 en DER no confiable, una estructura ASN.1 profundamente anidada y manipulada puede agotar la pila del proceso y bloquear la aplicación. Tenga en cuenta que el backend libcrypto (OpenSSL) no utiliza el asistente de validación ASN.1 de picotls y, por lo tanto, es inmune a esta vulnerabilidad. La vulnerabilidad ha sido abordada en el commit c14231d801407640bc42c2dcf92783409ea6a7c7. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 25, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-45271', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-25T14:18:20.428853Z'} -
New CVE Received by [email protected]
Aug. 21, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'h2o', 'product': 'picotls', 'versions': [{'status': 'affected', 'version': '< c14231d801407640bc42c2dcf92783409ea6a7c7'}]}] Added 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. Added CVSS V3.1 AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Added CWE CWE-835 Added Reference https://github.com/h2o/picotls/commit/c14231d801407640bc42c2dcf92783409ea6a7c7 Added Reference https://github.com/h2o/picotls/security/advisories/GHSA-84f5-m5x2-82q4