# CVE-2026-23490: pyasn1 memory exhaustion DoS in OID decoder

Source: https://junglewise.ai/threats/cve-2026-23490-pyasn1-memory-exhaustion-dos-in-oid-decoder  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-01-16. Updated: 2026-07-21  
License: CC BY 4.0 with a link back

CVE-2026-23490 · Severity: high · CVSS 7.5 · Published 2026-01-16

A denial-of-service vulnerability exists in the pyasn1 library, which is used to handle ASN.1 data in various Python applications. By sending a specially crafted, malformed data packet (such as a malicious security certificate), an attacker can cause the application to consume excessive amounts of memory. This can lead to system crashes, service outages, or unresponsive applications in environments like LDAP servers and secure web endpoints.

Technologies: [Debian Linux](https://junglewise.ai/threats/technologies/debian), [Pyasn1](https://junglewise.ai/threats/technologies/pyasn1), [pyasn1 (PyPI)](https://junglewise.ai/threats/technologies/pypi-pyasn1). Vendors: [Debian](https://junglewise.ai/threats/vendors/debian), [Pyasn1](https://junglewise.ai/threats/vendors/pyasn1), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-23490 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-23490 being exploited in the wild.

**How severe is CVE-2026-23490?** High severity, with a CVSS score of 7.5, published 16 January 2026.

**Which products and versions are affected?** Pyasn1 < 0.6.2, 0.6.1; pyasn1 (PyPI) ECOSYSTEM:introduced=0.6.1,fixed=0.6.2.

**Is there a fix for CVE-2026-23490?** Yes. pyasn1 (PyPI): upgrade to 0.6.2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-23490 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-23490?** Check whether you run Debian Linux, Pyasn1 or pyasn1 (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- pyasn1 (PyPI): upgrade to 0.6.2 or later

  ```sh
  pip install "pyasn1>=0.6.2"
  ```


## Technical details

A Denial-of-Service (DoS) vulnerability exists in pyasn1 v0.6.1 due to improper handling of RELATIVE-OID values during BER/DER decoding. The root cause is an integer handling issue in the decoder component where malformed RELATIVE-OID values containing excessive continuation octets lead to massive memory allocation. An unauthenticated remote attacker can exploit this by providing a crafted ASN.1 structure (e.g., within an X.509 certificate or LDAP request) that the library attempts to decode. This results in memory exhaustion and process termination. The issue is addressed in version 0.6.2 by implementing limits on the allowed bytes in the decoder.

## Affected products

- pyasn1 pyasn1 0.6.1

## Identifiers

- CVE-2026-23490
- GHSA-63vm-454h-vhhq
- PYSEC-2026-1810

## Timeline

- 2026-01-16: advisory: GitHub Advisory GHSA-63vm-454h-vhhq published
- 2026-01-16: patched: Version 0.6.2 released

## References

- [https://api.github.com/users/tsigouris007](https://api.github.com/users/tsigouris007)
- [https://github.com/tsigouris007](https://github.com/tsigouris007)
- [https://api.github.com/users/tsigouris007/gists%7B/gist_id%7D](https://api.github.com/users/tsigouris007/gists%7B/gist_id%7D)
- [https://api.github.com/users/tsigouris007/repos](https://api.github.com/users/tsigouris007/repos)
- [https://avatars.githubusercontent.com/u/10864434?v=4](https://avatars.githubusercontent.com/u/10864434?v=4)
- [https://api.github.com/users/tsigouris007/events%7B/privacy%7D](https://api.github.com/users/tsigouris007/events%7B/privacy%7D)

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