glibc: Out-of-bounds Read
CVE-2026-4437 is a high-severity out-of-bounds read vulnerability in glibc from The GNU C Library, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected glibc versions: 2.34 through 2.43. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.34% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update SIMATIC S7-1500 CPU 1518-4 PN/DP MFP to V3.1.6 or a later version.
- Update SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP to V3.1.6 or a later version.
- Update SIPLUS S7-1500 CPU 1518-4 PN/DP MFP to V3.1.6 or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| The GNU C Library | glibc | 2.34 through 2.43 | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP | V3.1.5 up to, but not including, V3.1.6 | V3.1.6 |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP | V3.1.5 up to, but not including, V3.1.6 | V3.1.6 |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP | V3.1.5 up to, but not including, V3.1.6 | V3.1.6 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CISA (ADP).
Official description
Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C Library version 2.34 to version 2.43 could, with a crafted response from the configured DNS server, result in a violation of the DNS specification that causes the application to treat a non-answer section of the DNS response as a valid answer.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Out-of-bounds Read
The product reads data past the end, or before the beginning, of the intended buffer.
How developers prevent this class of flaw
- Use a language that provides appropriate memory abstractions.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- sourceware.org/bugzilla/show_bug.cgi?id=34014Exploit, Issue Tracking
Other references
Other vulnerabilities in glibc
- 7.0 High severity
- 7.7 High severity
- 7.3 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.5 High severity
Recent Out-of-bounds Read vulnerabilities
- 7.5 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
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