CVE-2018-20784: canonical ubuntu_linux Loop with Unreachable Exit Condition
Vulnerability summary
CVE-2018-20784 is a critical (CVSS 9.8) Loop with Unreachable Exit Condition vulnerability in canonical ubuntu_linux. EPSS estimates a 4.17% chance of exploitation in the next 30 days, higher than 90.9% of scored vulnerabilities.
Severe, CVSS 9.8 (NVD); no exploitation reported by the 5 checked sources; EPSS 4% (FIRST, 04-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 10 · Related 8Timeline
- 22-02-2019PublishedVulnerability first disclosed.
- 05-08-2024Last modifiedVulnerability information updated.
Description
In the Linux kernel before 4.20.2, kernel/sched/fair.c mishandles leaf cfs_rq's, which allows attackers to cause a denial of service (infinite loop in update_blocked_averages) or possibly have unspecified other impact by inducing a high load.
CVSS metrics
5 scores · 3 sources · 3 versions- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
4.17%
Chance of exploitation in the next 30 days
Percentile
91%
Versus all other CVEs
30-day change
No change 0.00 pp
From 4.17% on 05-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu23 products
- linux< 4.4.0-170.199 | < 4.15.0-60.67
- linux-aws< 4.4.0-1059.63 | < 4.4.0-1099.110 | < 4.15.0-1047.49
- linux-aws-fips< 4.15.0-2018.18 | All versions (No fix recorded)
- linux-aws-hwe< 4.15.0-1047.49~16.04.1
- linux-azure< 4.15.0-1059.64~14.04.1 | < 4.15.0-1056.61 | < 5.0.0-1014.14~18.04.1
Redhat2 products
Canonical1 product
- ubuntu_linuxEOL14.04 | 16.04 | 18.04
Debian1 product
- linux< 4.19.16-1
Linux1 product
- linux_kernel≥ 4.13, < 4.14.93 | ≥ 4.19, < 4.19.15 | ≥ 4.20, < 4.20.2 | 5.0:rc1
5 vendors · 28 products
References
17 links- github.com/torvalds/linux/commit/c40f7d74c741a907cfaeb73a7697081881c497d0X Refsource MISCPatchThird Party AdvisoryREPORT
- cdn.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.20.2X Refsource MISCRelease NotesVendor AdvisoryREPORT
