Vulnerability · Published Oct 29, 2026 · Assigned by GitHub_M
CVE-2026-119195pyasn1: Quadratic-time denial of service in constructed string and indefinite-length ANY decoding
High 7.5
In plain English
A high-severity security flaw in pyasn1 from pyasn1. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, constructed string and indefinite-length ANY decoding repeatedly concatenates each fragment onto a growing bytes value. Attacker-controlled BER or CER data can use many constructed OCTET STRING or character-string fragments. DER rejects constructed OCTET STRING without a schema, but accepts its definite-length form when asn1Spec selects univ.OctetString; it also accepts constructed character strings such as UTF8String without a schema, even though those encodings are not valid DER. The separate indefinite-length ANY path is reachable in BER and CER when asn1Spec selects univ.Any; DER rejects indefinite lengths. OctetStringPayloadDecoder uses growing header concatenation and AnyPayloadDecoder.indefLenValueDecoder uses growing chunk concatenation, repeatedly copying an increasing prefix and causing quadratic work. A sufficiently fragmented value can occupy decoding workers and cause CPU exhaustion without confidentiality or integrity impact. This issue is fixed in version 0.6.5.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | pyasn1 | no fix listed | DEBIAN-CVE-2026-119195 |
| Debian:13 | pyasn1 | no fix listed | DEBIAN-CVE-2026-119195 |
| Debian:14 | pyasn1 | 0.6.5-1 | DEBIAN-CVE-2026-119195 |
| PyPI | pyasn1 | 0.6.5 | GHSA-9m75-vc3g-4x39 |
| Ubuntu:22.04:LTS | pyasn1 | no fix listed | UBUNTU-CVE-2026-119195 |
| Ubuntu:24.04:LTS | pyasn1 | no fix listed | UBUNTU-CVE-2026-119195 |
| Ubuntu:26.04:LTS | pyasn1 | no fix listed | UBUNTU-CVE-2026-119195 |
| Ubuntu:26.10 | pyasn1 | no fix listed | UBUNTU-CVE-2026-119195 |
Affected products (as reported)
Weakness: CWE-407 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/pyasn1/pyasn1/security/advisories/GHSA-9m75-vc3g-4x39 x_refsource_CONFIRM
- https://github.com/pyasn1/pyasn1/pull/132 x_refsource_MISC
- https://github.com/pyasn1/pyasn1/commit/4ce00797c594b59c1fd6b86d9ebc3ba87b7ec9f9 x_refsource_MISC
- https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5 x_refsource_MISC