CVE-2026-59884: pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs
Vulnerability summary
CVE-2026-59884 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in pyasn1. EPSS estimates a 0.62% chance of exploitation in the next 30 days, higher than 49.5% of scored vulnerabilities.
Severe, CVSS 7.5 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 10 · Related 9Timeline
- 14-07-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths. Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.
CVSS metrics
7 scores · 7 sources · 1 version- OSV · PypiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · WolfiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · ChainguardEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.62%
Chance of exploitation in the next 30 days
Percentile
50%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.62% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard31 products
- airflow-2All versions (No fix recorded)
- airflow-3< 3.3.0-r4
- airflow-3-iamguarded-compatAll versions (No fix recorded)
- apache-beam-python-3.12-sdk< 2.75.0-r1
- authentik-2026.2< 2026.2.6-r11
Wolfi13 products
- airflow-3< 3.3.0-r4
- airflow-3-iamguarded-compatAll versions (No fix recorded)
- datadog-agent-7.72-core-integrationsAll versions (No fix recorded)
- datadog-agent-7.75-core-integrationsAll versions (No fix recorded)
- kserve< 0.20.0-r7
Debian1 product
- pyasn1< 0.4.8-3+deb12u3 | < 0.6.1-1+deb13u3 | < 0.6.4-1
Pyasn11 product
- pyasn1< 0.6.4
PyPI1 product
- pyasn1< 0.6.4
Ubuntu1 product
- pyasn1All versions (No fix recorded) | < 0.4.8-1ubuntu0.3 | < 0.4.8-4ubuntu0.3 | < 0.6.3-1ubuntu0.1
6 vendors · 48 products
References
11 links- github.com/pyasn1/pyasn1/security/advisories/GHSA-m4p7-r5rc-7g4jX Refsource CONFIRMWEBAdvisoryREPORTThird Party Advisory
- github.com/pyasn1/pyasn1PACKAGE
