CVE-2026-59885 pyasn1 CVE debrief

Who should care

Users of pyasn1 library, especially those who decode untrusted ASN.1 data, should be aware of this vulnerability and take necessary actions to mitigate the risk. This includes updating to version 0.6.4 or later, implementing input validation and sanitization, and monitoring for suspicious ASN.1 decoding activity. Additionally, security teams and vulnerability management teams should prioritize this vulnerability and ensure that affected systems are properly patched or mitigated.

Technical summary

The BER, CER, and DER decoders in pyasn1 process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs. This can lead to excessive CPU consumption and denial of service attacks when decoding untrusted ASN.1 data. The encoders also exhibit the same quadratic behavior when re-encoding previously decoded attacker-supplied values. To mitigate this vulnerability, it is essential to update pyasn1 to version 0.6.4 or later and implement input validation and sanitization for ASN.1 data.

Defensive priority

High priority should be given to updating pyasn1 to version 0.6.4 or later, especially for applications that decode untrusted ASN.1 data. Additionally, implementing input validation and sanitization, monitoring for suspicious activity, and reviewing compensating controls are crucial to mitigating this vulnerability.

Recommended defensive actions

• Update pyasn1 to version 0.6.4 or later
• Implement input validation and sanitization for ASN.1 data
• Monitor for suspicious ASN.1 decoding activity
• Consider using alternative ASN.1 libraries
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record was published on 2026-07-14T17:17:14.880Z and was last modified on 2026-07-21T14:38:21.580Z. The NVD entry is currently Analyzed. This information is based on the provided source corpus and may not reflect the full scope of the vulnerability. Further verification is recommended to ensure accurate understanding of the vulnerability's impact.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.