CVE-2025-61661: gnu grub2 Incorrect Calculation of Buffer Size
Vulnerability summary
CVE-2025-61661 is a medium (CVSS 4.8) Incorrect Calculation of Buffer Size vulnerability in gnu grub2. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 8.4% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 11 · Related 11Timeline
- 18-11-2025PublishedVulnerability first disclosed.
- 01-09-2026Last modifiedVulnerability information updated.
Description
A vulnerability has been identified in the GRUB (Grand Unified Bootloader) component. This flaw occurs because the bootloader mishandles string conversion when reading information from a USB device, allowing an attacker to exploit inconsistent length values. A local attacker can connect a maliciously configured USB device during the boot sequence to trigger this issue. A successful exploitation may lead GRUB to crash, leading to a Denial of Service. Data corruption may be also possible, although given the complexity of the exploit the impact is most likely limited.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated4.8MediumCVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
- OSV · DebianEcosystem advisory · calculated4.8MediumCVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
- NVDNIST4.8MediumCVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
EPSS trend
Probability
0.19%
Chance of exploitation in the next 30 days
Percentile
8%
Versus all other CVEs
30-day change
0.00 pp
From 0.19% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Ubuntu3 products
- grub2All versions (No fix recorded)
- grub2-signedAll versions (No fix recorded)
- grub2-unsignedAll versions (No fix recorded)
Debian1 product
- grub2All versions (No fix recorded) | < 2.14-1
Gnu1 product
- grub2≤ 2.14
3 vendors · 5 products
