# pyasn1: Uncontrolled resource consumption when converting decoded REAL values

Advisory record · `GHSA-hm4w-wwcw-mr6r`

- **Identifiers:** `GHSA-hm4w-wwcw-mr6r` · `CVE-2026-59886` · `PYSEC-2026-3457`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-770](https://cwe.mitre.org/data/definitions/770.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 21 Jul 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 21 Jul 2026, 19:11 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `pyasn1` (PyPI): affected `<0.6.4`; fixed in `0.6.4`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Affected are pyasn1 versions before 0.6.4, where converting a decoded REAL value to a float can take excessive CPU and memory, hanging the process. An attacker only needs to supply a short encoded REAL value with a very large exponent to untrusted decoders, and the hang occurs when the decoded value is printed, compared, or converted to float; decoding alone does not trigger it. Upgrade to pyasn1 0.6.4 or later, which fixes the issue.

Written 5 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0044, the 38th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:35 UTC: First seen by agentprime
- 31 Oct 2026, 14:35 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-hm4w-wwcw-mr6r)

## Sources

- [GitHub Advisory Database: GHSA-hm4w-wwcw-mr6r](https://github.com/advisories/GHSA-hm4w-wwcw-mr6r)
- [OSV: GHSA-hm4w-wwcw-mr6r](https://osv.dev/vulnerability/GHSA-hm4w-wwcw-mr6r)
- <https://github.com/pyasn1/pyasn1/security/advisories/GHSA-hm4w-wwcw-mr6r>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-59886>
- <https://github.com/pyasn1/pyasn1/commit/e60c691cb91addb8fcefa2f537e85ede6fb1e886>
- <https://github.com/pyasn1/pyasn1>
- <https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-hm4w-wwcw-mr6r>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-hm4w-wwcw-mr6r/>. Everything for agents: <https://agentprime.io/llms.txt>.