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.
CVE-2026-59884
This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 72% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EG Risk
- 49(Track)EG Risk 49/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity75% × 45%Exploitation0% × 40%Automatability100% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 28%
- KEV
- Not listed
Published
July 14, 2026
Last Modified
July 21, 2026
Advisory Details (3)
Auto-updated Jul 15, 2026pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs · Advisory · pyasn1/pyasn1 · GitHub
Affected: 0.6.4. Long-form tag IDs are now limited to 20 octets (140-bit tag IDs, matching
https://github.com/pyasn1/pyasn1/security/advisories/GHSA-m4p7-r5rc-7g4jRelease 0.6.4
Patch available: pyasn1/pyasn1 v0.6.4
https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4commit 628e36ecbb52 (pyasn1/pyasn1)
Patch available: pyasn1/pyasn1 v0.6.4 (contains commit 628e36ecbb52)
https://github.com/pyasn1/pyasn1/commit/628e36ecbb5277a3f01572ce418ef54271b165a5Vendor Advisories for CVE-2026-59884(3)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- GHSA-m4p7-r5rc-7g4jGitHub Security AdvisoriesHigh
pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs
- CVE-2026-59884Microsoft Security Response Center (MSRC)High
pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs
- RHSA-2026:40236Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update
Patch Availability(1)
| Vendor / Ecosystem | Fixed in / Patch | Released | Source |
|---|---|---|---|
| redhat | jaeger-main-2.19.0-1.1.hum1 | 2026-07-15 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 20× in last 7d / 28× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-27 14:14 UTCEPSS rescore
- 2026-07-27 11:02 UTCVendor advisory
- 2026-07-26 23:24 UTCEG score recompute
- 2026-07-26 23:24 UTCVendor advisory
- 2026-07-26 14:54 UTCEPSS rescore
- 2026-07-26 14:54 UTCEPSS rescore
- 2026-07-26 11:44 UTCEG score recompute
- 2026-07-26 11:44 UTCVendor advisory
- 2026-07-25 14:18 UTCEPSS rescore
- 2026-07-25 14:18 UTCEPSS rescore
- 2026-07-24 14:18 UTCEPSS rescore
- 2026-07-24 14:18 UTCEPSS rescore
- 2026-07-23 14:18 UTCEPSS rescore
- 2026-07-23 14:18 UTCEPSS rescore
- 2026-07-23 03:21 UTCEG score recompute
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-21 15:25 UTCEPSS rescore
- 2026-07-20 17:08 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 02:29 UTCEPSS rescore
- 2026-07-18 10:04 UTCEPSS rescore
- 2026-07-16 17:03 UTCEPSS rescore
- 2026-07-15 16:57 UTCEPSS rescore
Show 3 moreShow fewer
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-14 17:16 UTCEG score recompute
- 2026-07-14 17:10 UTCMITRE cvelistV5first tracked
Frequently asked(5)
What is CVE-2026-59884?
When was CVE-2026-59884 disclosed?
Is CVE-2026-59884 actively exploited?
What is the CVSS score of CVE-2026-59884?
How do I remediate CVE-2026-59884?
Dependency Blast Radius
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