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CVE-2025-38614

eventpoll: Fix semi-unbounded recursion

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 2.6.33, 2.6.34, 2.6.35, 2.6.36, 2.6.38, and 6 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e · fixed in 71379495ab70eaba19224bd71b5b9b399eb85e04; From 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e · fixed in 1b13b033062824495554e836a1ff5f85ccf6b039; From 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e · fixed in 2a0c0c974bea9619c6f41794775ae4b97530e0e6; From 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e · fixed in 7a2125962c42d5336ca0495a9ce4cb38a63e9161; From 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e · fixed in ea5f97dbdcb1651581a22bd10afd2f0dd9dc11d6; From 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e · fixed in 3542c90797bc3ab83ebab54b737d751cf3682036; From 22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e · fixed in f2e467a48287c868818085aa35389a224d226732; From 2.6.32.30 · fixed in 2.6.33; From 2.6.33.8 · fixed in 2.6.34; From 2.6.34.10 · fixed in 2.6.35; From 2.6.35.12 · fixed in 2.6.36; From 2.6.37.3 · fixed in 2.6.38

  • Linux Linux

    2.6.38

  • KernelLinux

    From 2.6.38 · fixed in 5.15.190; From 5.16.0 · fixed in 6.1.149; From 6.2.0 · fixed in 6.6.103; From 6.7.0 · fixed in 6.12.43; From 6.13.0 · fixed in 6.15.11; From 6.16.0 · fixed in 6.16.1

References 7

git.kernel.org