CVE-2021-3998: gnu glibc Out-of-bounds Read
Vulnerability summary
CVE-2021-3998 is a high (CVSS 7.5) Out-of-bounds Read vulnerability in gnu glibc. EPSS estimates a 2.20% chance of exploitation in the next 30 days, higher than 82.5% of scored vulnerabilities.
Severe, CVSS 7.5 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 2% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 2Timeline
- 24-08-2022PublishedVulnerability first disclosed.
- 14-10-2026Last modifiedVulnerability information updated.
Description
A flaw was found in glibc. The realpath() function can mistakenly return an unexpected value, potentially leading to information leakage and disclosure of sensitive data.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS trend
Probability
2.20%
Chance of exploitation in the next 30 days
Percentile
83%
Versus all other CVEs
30-day change
Increase +0.45 pp
From 1.76% 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: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Debian1 product
- glibc< 2.33-4
Gnu1 product
- glibc≥ 2.33, < 2.35
Ubuntu1 product
- glibc< 2.35-0ubuntu1
4 vendors · 9 products
References
14 links- access.redhat.com/security/cve/CVE-2021-3998Third Party Advisory
- security.netapp.com/advisory/ntap-20221020-0003/Third Party Advisory
