USN-8539-1: GnuTLS vulnerabilities
Haruto Kimura discovered that GnuTLS did not properly apply permitted name constraints in certain certificate validation paths. A remote attacker could possibly use this issue to bypass certificate validation, leading to a machine-in-the-middle attack. (CVE-2026-42011) Oleh Konko discovered that GnuTLS incorrectly fell back to Common Name checks for certain URI and SRV subject alternative names. A remote attacker could possibly use this issue to bypass certificate validation, leading to a machine-in-the-middle attack. (CVE-2026-42012) Haruto Kimura and Joshua Rogers discovered that GnuTLS incorrectly fell back to Common Name checks when subject alternative names were oversized. A remote attacker could possibly use this issue to bypass certificate validation, leading to a machine-in-the-middle attack. (CVE-2026-42013) Luigino Camastra and Joshua Rogers discovered that GnuTLS had a use-after-free issue when changing PKCS#11 token security officer PINs in certain cases. An attacker could possibly use this issue to cause GnuTLS to crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-42014) Zou Dikai discovered that GnuTLS did not properly validate PKCS#12 bag sizes in certain cases. An attacker could possibly use this issue to cause GnuTLS to crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-42015)
CSIRTS triage
- What
- GnuTLS has vulnerabilities that could allow remote attackers to bypass certificate validation.
- Who is affected
- Deployments of GnuTLS are affected.
- Urgency
- Remediation is urgent due to the risk of machine-in-the-middle attacks.
- Action
- Update to the latest version of GnuTLS.
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Details
Original advisory: https://ubuntu.com/security/notices/USN-8539-1
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-2026-420110.47% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 39% of all scored CVEs.
- Low exploitation riskCVE-2026-420120.35% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 28% of all scored CVEs.
- Low exploitation riskCVE-2026-420130.42% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 35% of all scored CVEs.
- Low exploitation riskCVE-2026-420140.15% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 5% of all scored CVEs.
- Low exploitation riskCVE-2026-420150.73% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 51% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-42011 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-42012 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-42013 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-42014 | coverage & exploitation status | NVD · CVE.org |
| CVE-2026-42015 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
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