CVE-2026-59884: Cve bin tool · pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs
Affects cve-bin-toolSource GCVE Database
Not known to be exploited · CVSS 7.5 High : upgrade to 3.4_1 soon.
Data as of 1 Nov 2026, 01:39 UTC
- Patch
- Available – fixed in 3.4_1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.
What to do
Upgrade cve-bin-tool to 3.4_1.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewcve-bin-toolpkg:brew/cve-bin-toolOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available in pyasn1 version 3.4_1, which limits long-form tag IDs to 20 octets and rejects oversized tags with PyAsn1Error. Users should upgrade to this version or later. As a workaround, applications can bound the size of untrusted input passed to the decode() function to prevent processing excessively large tag IDs.
Description
CVE-2026-59884 is a denial of service vulnerability in the pyasn1 library's BER/CER/DER decoders caused by unbounded long-form tag IDs. The decoder accumulates continuation octets without an upper limit, allowing crafted inputs to cause excessive CPU consumption. On Python 3.11 and later, this can also trigger an unhandled ValueError during error message formatting, potentially bypassing error handling. The issue affects decoding of untrusted BER/CER/DER inputs and was fixed in pyasn1 version 3.4_1 by limiting tag IDs to 20 octets and rejecting oversized tags.
References
- github.com/pyasn1/pyasn1/security/advisories/GHSA-m4p7-r5rc-7g4j (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-59884 (opens in a new tab)
- github.com/pyasn1/pyasn1/commit/628e36ecbb5277a3f01572ce418ef54271b165a5 (opens in a new tab)
- github.com/pyasn1/pyasn1 (opens in a new tab)
- github.com/pyasn1/pyasn1/releases/tag/v0.6.4 (opens in a new tab)
- github.com/pypa/advisory-database/tree/main/vulns/pyasn1/PYSEC-2026-3455.yaml (opens in a new tab)