# CVE-2026-77761: Cross-Document Parser State Contamination in misp-stix

> Attackers can contaminate MISP events with data from previous STIX documents via parser state reuse, causing data leakage and integrity issues.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 21 Aug 2026
- **Updated:** 21 Aug 2026
- **Also known as:** GHSA-q62h-w723-22p2

## What is CVE-2026-77761?

CVE-2026-77761 is a medium-severity vulnerability in misp-stix, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A parser state isolation vulnerability in misp-stix could cause data from a previously processed STIX document to be retained and incorporated into the MISP event generated from a subsequent document when the same parser instance is reused.

Several STIX 1 and STIX 2 parser components maintained per-document state that was not completely cleared between conversions. In the STIX 2 parser, galaxy and galaxy-cluster information, including custom galaxy clusters, could survive a parser reset and subsequently be associated with objects from another bundle.

The STIX 1 parsers were affected by the same underlying state-management issue. Depending on the parser type, retained information could include galaxies, references, passive DNS bookkeeping, package titles, dates, and timestamps. As a result, parsing a second STIX package with an already-used parser could produce a MISP event containing information that was present only in the previously processed package. For example, a generated event could inherit passive DNS records from an earlier document, reference unrelated galaxy information, combine titles from different packages, or use timestamps originating from another conversion.

The issue primarily affects applications using the misp-stix API directly and reusing parser instances across independent STIX documents. Normal conversion entry points that instantiate a new parser for each file are not affected by this particular reuse scenario.

An attacker able to influence documents processed by such a long-lived parser could potentially cause information from one conversion to contaminate a subsequent MISP event. This can affect the integrity of generated threat intelligence, resulting in incorrect associations, misleading contextual information, or unrelated indicators being attributed to an event. In environments where consecutive documents have different access controls or distribution scopes, the retained state could additionally result in limited disclosure of information from a previously processed document.

Successful exploitation depends on the consuming application reusing the same parser instance and on the ordering of processed documents, which increases attack complexity. No direct availability impact or code execution is involved.

Weakness: CWE-459 (Incomplete Cleanup)

## Which versions are affected by CVE-2026-77761?


## How do I fix CVE-2026-77761?

No fix has been published for CVE-2026-77761 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-77761 being exploited?

There is no known exploitation of CVE-2026-77761 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77761 and fix it if it is affected.

What it is: CVE-2026-77761 is a medium-severity vulnerability in misp-stix, published on 21 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77761 in the wild and no public exploit code.

Affected product: misp-stix. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77761/ (Markdown: https://insights.sbomify.com/CVE-2026-77761/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77761
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77761
- OSV: https://osv.dev/vulnerability/CVE-2026-77761

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77761/
Summaries are generated and may contain mistakes; the official description above is the record.