# CVE-2026-119195: pyasn1: Quadratic-time denial of service in constructed string and indefinite-length ANY decoding

CVE-2026-119195 is fixed in pyasn1 on 1 platform by DEBIAN-CVE-2026-119195 (version 0.6.5-1), released November 3, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-119195
- Priority: High
- CVSS: 7.5 (Important)
- EPSS: 0.0053
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 29, 2026
- Weakness: Inefficient Algorithmic Complexity
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-119195

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | pyasn1 Debian 14 | 0.6.5-1 | [DEBIAN-CVE-2026-119195](https://patchblox.com/security/data/fix/linux/debian-cve-2026-119195.md) | Nov 3, 2026 |

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Data as of 2026-11-09T13:31:49Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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