CVE-2020-25597: fedoraproject fedora
Vulnerability summary
CVE-2020-25597 is a medium (CVSS 6.5) vulnerability in fedoraproject fedora. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 29.6% of scored vulnerabilities.
Not severe (CVSS 6.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 12 · Related 11Timeline
- 23-09-2020PublishedVulnerability first disclosed.
- 04-08-2024Last modifiedVulnerability information updated.
Description
An issue was discovered in Xen through 4.14.x. There is mishandling of the constraint that once-valid event channels may not turn invalid. Logic in the handling of event channel operations in Xen assumes that an event channel, once valid, will not become invalid over the life time of a guest. However, operations like the resetting of all event channels may involve decreasing one of the bounds checked when determining validity. This may lead to bug checks triggering, crashing the host. An unprivileged guest may be able to crash Xen, leading to a Denial of Service (DoS) for the entire system. All Xen versions from 4.4 onwards are vulnerable. Xen versions 4.3 and earlier are not vulnerable. Only systems with untrusted guests permitted to create more than the default number of event channels are vulnerable. This number depends on the architecture and type of guest. For 32-bit x86 PV guests, this is 1023; for 64-bit x86 PV guests, and for all ARM guests, this number is 4095. Systems where untrusted guests are limited to fewer than this number are not vulnerable. Note that xl and libxl limit max_event_channels to 1023 by default, so systems using exclusively xl, libvirt+libxl, or their own toolstack based on libxl, and not explicitly setting max_event_channels, are not vulnerable.
CVSS metrics
5 scores · 4 sources · 2 versions- OSV · AlpineEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
EPSS trend
Probability
0.36%
Chance of exploitation in the next 30 days
Percentile
30%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.36% on 04-10-2026
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: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Alpine1 product
- xen≥ 4.4.0, < 4.12.3-r4 | ≥ 4.4.0, < 4.13.1-r4 | ≥ 4.4.0, < 4.14.0-r1 | ≥ 4.4.0, < 4.11.4-r2
Debian1 product
- xen< 4.14.0+80-gd101b417b7-1
Fedoraproject1 product
- fedoraEOL31
Ubuntu1 product
- xenAll versions (No fix recorded) | < 4.11.3+24-g14b62ab3e5-1ubuntu2.3
Xen1 product
- xen≥ 4.4.0, ≤ 4.14.0
5 vendors · 5 products
References
12 links
- lists.opensuse.org/opensuse-security-announce/2020-10/msg00008.htmlVendor AdvisoryX Refsource SUSEMailing ListThird Party Advisory