USN-8611-1: GNU C Library vulnerabilities
It was discovered that the GNU C Library iconv function incorrectly handled certain IBM character sets. An attacker could possibly use this issue to cause a denial of service. (CVE-2026-4046) It was discovered that the GNU C Library DNS functions incorrectly handled certain DNS server responses when using gethostbyaddr or gethostbyaddr_r. An attacker in a privileged network position could possibly use this issue to cause an application to violate DNS specification or obtain incorrect hostname information. This issue only affected Ubuntu 24.04 LTS. (CVE-2026-4437, CVE-2026-4438) It was discovered that the GNU C Library deprecated debugging functions incorrectly enforced caller-supplied buffer lengths. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. (CVE-2026-5435) It was discovered that the GNU C Library scanf family of functions contained a heap buffer overflow when processing certain format specifiers. An attacker could possibly use this issue to cause a denial of service or execute arbitrary code. (CVE-2026-5450) It was discovered that the GNU C Library ungetwc function incorrectly handled certain character encodings. An attacker could possibly use this issue to obtain sensitive information or cause a denial of service. (CVE-2026-5928) It was discovered that the GNU C Library deprecated debugging functions incorrectly validated DNS response record data. An attacker could possibly use this issue to cause a denial of service or obtain sensitive information. (CVE-2026-6238)
CSIRTS triage
- What
- Multiple vulnerabilities in the GNU C Library could lead to denial of service, arbitrary code execution, or information disclosure.
- Who is affected
- Users of the GNU C Library on Ubuntu 24.04 LTS.
- Urgency
- Remediation is urgent due to the critical nature of the vulnerabilities and potential for exploitation.
- Action
- Update the GNU C Library to the latest patched version.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://ubuntu.com/security/notices/USN-8611-1
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-40460.38% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 31% of all scored CVEs.
- Low exploitation riskCVE-2026-44370.33% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 25% of all scored CVEs.
- Low exploitation riskCVE-2026-44380.32% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 24% of all scored CVEs.
- Low exploitation riskCVE-2026-54350.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all scored CVEs.
- Low exploitation riskCVE-2026-54500.50% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 40% of all scored CVEs.
- Low exploitation riskCVE-2026-59280.37% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 30% of all scored CVEs.
- Low exploitation riskCVE-2026-62380.36% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 29% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-4046 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-4437 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-4438 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-5435 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-5450 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-5928 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-6238 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- critical[UPDATE] [critical] GNU libc: Multiple vulnerabilitiescert-bund
- medium[UPDATE] [medium] GNU libc: Multiple vulnerabilitiescert-bund
- medium[UPDATE] [medium] GNU libc: Vulnerability allows denial of servicecert-bund
- medium[UPDATE] [medium] GNU libc: Multiple vulnerabilities allow manipulation of DNS responsescert-bund
More from Ubuntu Security Notices
- highUSN-8620-4: Linux kernel (Intel IoTG) vulnerabilities2026-07-31
- highUSN-8620-3: Linux kernel (Intel IoTG) vulnerabilities2026-07-31
- unknownUSN-8625-1: OpenSSL vulnerability2026-07-30
- unknownUSN-8624-1: Sinatra vulnerability2026-07-29
- unknownUSN-8623-1: Linux kernel (NVIDIA) vulnerabilities2026-07-29