Vulnerability · CVE-2026-119194
pyasn1 has quadratic CPU use in schemaless BER/CER/DER container decoding
Published Oct 30, 2026 · catalog updated Oct 30, 2026 · pyasn1 has quadratic CPU
Last checked Nov 6, 2026. A connected source was read within the last 7 days.
Check if you run it
No confirmed exploitation is on record for CVE-2026-119194. EPSS is 0.43%. Act only if a listed version of pyasn1 has quadratic CPU is installed.
Gaps on this record
- The stored product name is a package slug. The name on this page is taken from the title (pyasn1 has quadratic CPU).
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- High7.5
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.43%
- Remediation
- Version ranges on file
- Affected products
- PyPI pyasn1 · pip pyasn1 · pypi pyasn1
### Summary When an application decodes attacker-controlled BER, CER, or DER data without an ASN.1 schema, a container with many distinct long tag IDs can cause quadratic CPU use. Repeated inputs can exhaust CPU and reduce service availability. ### Details ConstructedPayloadDecoderBase._decodeComponentsSchemaless inserts every decoded component’s TagSet into a growing set, although it only needs to distinguish one tag set from two or more. Attacker-chosen tag IDs can have colliding TagSet hashes, making each later insertion compare against an increasing number of earlier tags. This path is present in v0.6.4 and is inherited by the CER and DER decoders. The proposed fix stops growing the classification set after it contains two distinct tag sets, while retaining every decoded component and its order. On v0.6.4 with CPython 3.12.10, increasing the collision input from 3,200 to 6,400 components raised decode CPU time from 0.438 to 1.747 seconds; a comparable control rose from 0.031 to 0.065 seconds. Both inputs decoded successfully with the expected values and an empty remainder. ### Proof of concept Run this outside the repository checkout in a fresh Python 3.12 environment with pyasn1==0.6.4 installed: ### Impact Applications that pass attacker-controlled bytes to schemaless BER, CER, or DER decoding can spend disproportionate CPU time on a relatively small, valid input. The demonstrated impact is availability; no confidentiality or integrity impact was observed.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- PyPI pyasn10.3.3 → 0.6.5
- pip pyasn1>= 0.3.3, < 0.6.5
- pypi pyasn1version unspecified
How to fix CVE-2026-119194
Upgrade
CVE-2026-119194 lists a fix boundary at 0.6.5. Compare the installed build with that boundary before you change production.
Version check
Affected < 0.6.5
Advisory
Open the cve_org record and follow its fix.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-119194. EPSS is 0.43%. Act only if a listed version of pyasn1 has quadratic CPU is installed.
Which versions are affected?
Compare what you have installed with 0.3.3 → 0.6.5, >= 0.3.3, < 0.6.5. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-407. EPSS 0.43%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
Oct 30, 2026 · GitHub Advisory Database
Detected
### Summary When an application decodes attacker-controlled BER, CER, or DER data without an ASN.1 schema, a container with many distinct long tag IDs can cause quadratic CPU use. Repeated inputs can exhaust CPU and reduce service availability. ### Details ConstructedPayloadDecoderBase._decodeComponentsSchemaless inserts every decoded component’s TagSet into a growing set, although it only needs t
Oct 30, 2026 · GitHub Advisory Database
Updated
### Summary When an application decodes attacker-controlled BER, CER, or DER data without an ASN.1 schema, a container with many distinct long tag IDs can cause quadratic CPU use. Repeated inputs can exhaust CPU and reduce service availability. ### Details ConstructedPayloadDecoderBase._decodeComponentsSchemaless inserts every decoded component’s TagSet into a growing set, although it only needs t
Oct 30, 2026 · PyPA Advisory Database
Fix available
pyasn1 fixed in 0.6.5
Oct 30, 2026 · PyPA Advisory Database
Fix available
pyasn1 fixed in 0.6.5
Oct 30, 2026 · PyPA Advisory Database
Updated
### Summary When an application decodes attacker-controlled BER, CER, or DER data without an ASN.1 schema, a container with many distinct long tag IDs can cause quadratic CPU use. Repeated inputs can exhaust CPU and reduce service availability. ### Details ConstructedPayloadDecoderBase._decodeComponentsSchemaless inserts every decoded component’s TagSet into a growing set, although it only needs t
Sources
- CVE.orgVulnerability recordCVE-2026-119194
Official CVE identifier
cve.org - GitHub Advisory DatabasePackage advisoryGHSA-fm9c-5rcf-2q5p
pyasn1 has quadratic CPU use in schemaless BER/CER/DER container decoding
github.com - GitLab Advisory DatabasePackage advisoryCVE-2026-119194
When an application decodes attacker-controlled BER, CER, or DER data without an ASN.1 schema, a container with many distinct long tag IDs can cause quadratic CPU use. Repeated inputs can exhaust CPU and reduce service availability.
advisories.gitlab.com - PyPA Advisory DatabasePackage advisoryGHSA-fm9c-5rcf-2q5p
pyasn1 has quadratic CPU use in schemaless BER/CER/DER container decoding
osv.dev
References
Freshness
Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.
- GitHub Advisory DatabaseNov 6, 2026
- GitLab Advisory DatabaseNov 3, 2026
- PyPA Advisory DatabaseNov 2, 2026
- CVE.orgOct 31, 2026