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eventpoll: Fix semi-unbounded recursion (Linux Linux)

CVE-2025-38614
HIGH 7.8

At a glance

Source
NVD
EPSS
EPSS 0.18 % · percentile 8 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Modified

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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.

Weaknesses (CWE)

References

Scores

VersionScoreVectorScored by
CVSS 3.1HIGH 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HLinux
CVSS 3.1HIGH 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HNVD · 416baaa9-dc9f-4396-8d5f-8c081fb06d67 (Secondary)
CVSS 3.1MEDIUM 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HNVD · nvd@nist.gov (Primary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e < 71379495ab70eaba19224bd71b5b9b399eb85e04 ; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e < 1b13b033062824495554e836a1ff5f85ccf6b039 ; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e < 2a0c0c974bea9619c6f41794775ae4b97530e0e6 ; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e < 7a2125962c42d5336ca0495a9ce4cb38a63e9161 ; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e < ea5f97dbdcb1651581a22bd10afd2f0dd9dc11d6 ; affected 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e < 3542c90797bc3ab83ebab54b737d751cf3682036
Linux · Linuxaffected 2.6.38 ; unaffected 0 < 2.6.38 ; unaffected 5.15.190 ≤ 5.15.* ; unaffected 6.1.149 ≤ 6.1.* ; unaffected 6.6.103 ≤ 6.6.* ; unaffected 6.12.43 ≤ 6.12.*

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD