# CVE-2025-38614

## Summary

- **CVE ID:** CVE-2025-38614
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Aug 19, 2025
- **Last Modified:** Sep 8, 2026

## Description

In the Linux kernel, the following vulnerability has been resolved:

eventpoll: Fix semi-unbounded recursion

Ensure that epoll instances can never form a graph deeper than
EP_MAX_NESTS+1 links.

Currently, ep_loop_check_proc() ensures that the graph is loop-free and
does some recursion depth checks, but those recursion depth checks don't
limit the depth of the resulting tree for two reasons:

 - They don't look upwards in the tree.
 - If there are multiple downwards paths of different lengths, only one of
   the paths is actually considered for the depth check since commit
   28d82dc1c4ed ("epoll: limit paths").

Essentially, the current recursion depth check in ep_loop_check_proc() just
serves to prevent it from recursing too deeply while checking for loops.

A more thorough check is done in reverse_path_check() after the new graph
edge has already been created; this checks, among other things, that no
paths going upwards from any non-epoll file with a length of more than 5
edges exist. However, this check does not apply to non-epoll files.

As a result, it is possible to recurse to a depth of at least roughly 500,
tested on v6.15. (I am unsure if deeper recursion is possible; and this may
have changed with commit 8c44dac8add7 ("eventpoll: Fix priority inversion
problem").)

To fix it:

1. In ep_loop_check_proc(), note the subtree depth of each visited node,
and use subtree depths for the total depth calculation even when a subtree
has already been visited.
2. Add ep_get_upwards_depth_proc() for similarly determining the maximum
depth of an upwards walk.
3. In ep_loop_check(), use these values to limit the total path length
between epoll nodes to EP_MAX_NESTS edges.

## Affected Products

- Linux — Linux (22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e)
- Linux — Linux (8216e1a0d47cae06a75c42346f19dffe14e42d57)
- Linux — Linux (28a92748aa4bc57d35e7b079498b0ac2e7610a37)
- Linux — Linux (7eebcd4792c5a341559aed327b6afecbb1c46402)
- Linux — Linux (0eccd188cfeaf857a26f2d72941d27d298cf6a54)
- Linux — Linux (a72affdbb09f3f24f64ffcbbdf62c2e57c58f379)
- Linux — Linux (2.6.38)
- Linux — Linux (0)
- Linux — Linux (5.15.190)
- Linux — Linux (6.1.149)
- Linux — Linux (6.6.103)
- Linux — Linux (6.12.43)
- Linux — Linux (6.15.11)
- Linux — Linux (6.16.1)
- Linux — Linux (6.17)
- Linux — Linux (2.6.32.30)
- Linux — Linux (2.6.33.8)
- Linux — Linux (2.6.34.10)
- Linux — Linux (2.6.35.12)
- Linux — Linux (2.6.37.3)

## References

- [CNA](https://git.kernel.org/stable/c/71379495ab70eaba19224bd71b5b9b399eb85e04)
- [CNA](https://git.kernel.org/stable/c/1b13b033062824495554e836a1ff5f85ccf6b039)
- [CNA](https://git.kernel.org/stable/c/2a0c0c974bea9619c6f41794775ae4b97530e0e6)
- [CNA](https://git.kernel.org/stable/c/7a2125962c42d5336ca0495a9ce4cb38a63e9161)
- [CNA](https://git.kernel.org/stable/c/ea5f97dbdcb1651581a22bd10afd2f0dd9dc11d6)
- [CNA](https://git.kernel.org/stable/c/3542c90797bc3ab83ebab54b737d751cf3682036)
- [CNA](https://git.kernel.org/stable/c/f2e467a48287c868818085aa35389a224d226732)
- [CVE](https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-082556.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-032379.html)
- [siemens-SADP](https://cert-portal.siemens.com/productcert/html/ssa-019113.html)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.18%
- **EPSS Percentile:** 7.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-19._