# CVE-2026-64575: bpf: tcp: fix double sock release on batch realloc

> A double release bug in the Linux kernel's BPF TCP iterator causes a null pointer dereference and kernel panic when batch reallocation fails.

- **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:** 5 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-64575, DEBIAN-CVE-2026-64575, GHSA-f2rf-qgfg-8rxx, UBUNTU-CVE-2026-64575

## What is CVE-2026-64575?

CVE-2026-64575 is a high-severity use after free vulnerability in Linux, published on 5 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:

bpf: tcp: fix double sock release on batch realloc

bpf_iter_tcp_batch() releases the current batch via
bpf_iter_tcp_put_batch(), which drops the socket refs and rewrites
each slot with the socket cookie, then grows the batch. cur_sk/end_sk
are kept for bpf_iter_tcp_resume(), but on realloc failure the function
returns ERR_PTR() before resume runs, leaving cur_sk < end_sk over
slots that now hold cookies rather than sock pointers.
bpf_iter_tcp_seq_stop() then calls bpf_iter_tcp_put_batch() again and
dereferences a cookie as a struct sock.

Empty the batch on the failure path so stop() does not release it
again. The sockets were already freed by the first
bpf_iter_tcp_put_batch(), so nothing leaks, and a later read() rescans
the bucket from the start instead of skipping it. The sibling
GFP_NOWAIT failure path still holds real socket references and is left
for stop() to release.

  BUG: KASAN: null-ptr-deref in __sock_gen_cookie
  Read of size 8 at addr 0000000000000059 by task exploit
   ...
   __sock_gen_cookie (net/core/sock_diag.c:28)
   bpf_iter_tcp_put_batch (net/ipv4/tcp_ipv4.c:2918)
   bpf_iter_tcp_seq_stop (net/ipv4/tcp_ipv4.c:3270)
   bpf_seq_read (kernel/bpf/bpf_iter.c:205)
   vfs_read (fs/read_write.c:572)
   ksys_read (fs/read_write.c:716)
   do_syscall_64
   entry_SYSCALL_64_after_hwframe
  Kernel panic - not syncing: Fatal exception

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-64575?


## How do I fix CVE-2026-64575?

Apply the vendor's patch.

## Is CVE-2026-64575 being exploited?

There is no known exploitation of CVE-2026-64575 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64575 and fix it if it is affected.

What it is: CVE-2026-64575 is a high-severity use after free vulnerability in Linux, published on 5 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-2026-64575 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-2026-64575/ (Markdown: https://insights.sbomify.com/CVE-2026-64575/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64575
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64575
- OSV: https://osv.dev/vulnerability/CVE-2026-64575

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64575/
Summaries are generated and may contain mistakes; the official description above is the record.