# CVE-2026-89607: ecryptfs: reject oversized encrypted_key_size in parse_tag_3_packet

> A missing bounds check in the Linux kernel ecryptfs module allows out-of-bounds writes, potentially leading to code execution or privilege escalation.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100863, BELL-CVE-2026-89607, DEBIAN-CVE-2026-89607, GHSA-97r7-5j8w-q49j, UBUNTU-CVE-2026-89607

## What is CVE-2026-89607?

CVE-2026-89607 is a high-severity memory corruption vulnerability in Linux, published on 11 Sep 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:

ecryptfs: reject oversized encrypted_key_size in parse_tag_3_packet

parse_tag_3_packet() set encrypted_key_size from the Tag 3 packet body
without bounding it against ECRYPTFS_MAX_KEY_BYTES (64). When
encrypted_key_size > 64, decrypt_passphrase_encrypted_session_key()
sets decrypted_key_size = encrypted_key_size and performs two
out-of-bounds writes:

1. crypto_skcipher_decrypt() writes encrypted_key_size bytes into
   decrypted_key[64] via scatterlist, overflowing into the parent
   ecryptfs_auth_tok struct.
2. memcpy(crypt_stat->key, decrypted_key, decrypted_key_size) writes
   into crypt_stat->key[64], corrupting root_iv, keysig_list, and
   mutexes in ecryptfs_crypt_stat.

Only AES-192 (cipher code 0x08) enables this because it sets
crypt_stat->key_size = 24 independently of encrypted_key_size,
allowing crypto_skcipher_setkey() to succeed while encrypted_key_size
exceeds ECRYPTFS_MAX_KEY_BYTES.

The PKI decryption path (parse_tag_65_packet) already validates
decrypted_key_size <= ECRYPTFS_MAX_KEY_BYTES; the passphrase path
omits this check.

Bound encrypted_key_size against ECRYPTFS_MAX_KEY_BYTES (64) rather
than ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES (512). The 64-byte limit also
protects the 512-byte encrypted_key[] buffer, so the former 512-byte
check is removed as redundant.

[tyhicks: Adjust the code comment to refer to macros representing the
 buffer sizes rather than mentioning the buffer size values since they
 may change in the future]

## Which versions are affected by CVE-2026-89607?


## How do I fix CVE-2026-89607?

Apply the vendor's patch.

## Is CVE-2026-89607 being exploited?

There is no known exploitation of CVE-2026-89607 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89607 and fix it if it is affected.

What it is: CVE-2026-89607 is a high-severity memory corruption vulnerability in Linux, published on 11 Sep 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-2026-89607 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-2026-89607/ (Markdown: https://insights.sbomify.com/CVE-2026-89607/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89607
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89607
- OSV: https://osv.dev/vulnerability/CVE-2026-89607

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89607/
Summaries are generated and may contain mistakes; the official description above is the record.