# CVE-2026-74485: binfmt_misc: reject a flag character as the field delimiter

> An out-of-bounds read in the Linux kernel binfmt_misc module allows unprivileged users to trigger a crash or leak memory via a crafted registration string.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** AZL-95994, BELL-CVE-2026-74485, DEBIAN-CVE-2026-74485, GHSA-9rj7-pvjp-5h34, UBUNTU-CVE-2026-74485

## What is CVE-2026-74485?

CVE-2026-74485 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

binfmt_misc: reject a flag character as the field delimiter

The registration string starts with a user chosen delimiter that
separates the individual fields. So that the field parsers terminate
even on a truncated string create_entry() pads the buffer with that
same delimiter:

	memset(buf + count, del, 8);

Most fields are scanned for the delimiter with strchr()/scanarg() and
happily stop on the padding. The flags field is different: instead of
scanning for the delimiter check_special_flags() consumes the flag
characters 'P', 'O', 'C' and 'F' and stops at the first byte that is
none of them, relying on the trailing delimiter to end the scan.

If the delimiter is itself a flag character the padding no longer acts
as a terminator. The scan swallows all eight padding bytes and keeps
reading past the end of the allocation until it hits a byte that is
not a flag character. For example registering

	PaPEPPxPPiP

with 'P' as the delimiter (name "a", type extension, magic "x",
interpreter "i", empty flags) leaves the flag scan running off the end
of the buffer. The registration is rejected in the end because the
parser does not stop exactly at buf + count, but only after the out of
bounds read has already happened. With an unlucky allocation layout the
scan can walk into an unmapped page; under KASAN it is reported as a
slab out of bounds read. binfmt_misc mounts are available to
unprivileged users in a user namespace so the read is reachable without
privileges.

Reject a delimiter that is one of the flag characters up front. Such a
registration was always rejected anyway, only after the out of bounds
read, so no valid registration string changes meaning.

## Which versions are affected by CVE-2026-74485?


## How do I fix CVE-2026-74485?

Apply the vendor's patch.

## Is CVE-2026-74485 being exploited?

There is no known exploitation of CVE-2026-74485 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74485 and fix it if it is affected.

What it is: CVE-2026-74485 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74485 in the wild and no public exploit code.

Affected product: Linux. 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-2026-74485/ (Markdown: https://insights.sbomify.com/CVE-2026-74485/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74485
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74485
- OSV: https://osv.dev/vulnerability/CVE-2026-74485

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74485/
Summaries are generated and may contain mistakes; the official description above is the record.