Description
Initializing the DNS stub resolver from an /etc/resolv.conf file, or a LOCALDOMAIN environment variable, whose search list contains a domain of roughly 200 characters or more in the GNU C Library version 2.26 to 2.44 results in an assertion failure which aborts the process.
The resolver truncates the search list when copying it into the fixed-size _res.defdname buffer, then asserts that the copy is consistent with the full configuration. The consistency check compared against the wrong size and did not handle a first entry that does not fit, so a correctly truncated list failed the assertion. Any process that resolves names through the library is affected, including long-running processes that reload /etc/resolv.conf on the next query after it changes. Search domains are commonly written to /etc/resolv.conf from data received over DHCP or from a VPN server, so an attacker on the local network may be able to trigger this without privileges on the target system, subject to validation by the network configuration software.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| The GNU C Library | glibc | 2.26 – ≤ 2.44 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | glibc | 2.43-6 | — |
| Debian 13 | glibc | No fix yet | — |
| Debian 12 | glibc | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | glibc | 2.44-1ubuntu2.1 | USN-9065-1 |
| Ubuntu 26.04 LTS | glibc | 2.43-2ubuntu2.7 | USN-9065-1 |
| Ubuntu 24.04 LTS | glibc | 2.39-0ubuntu8.12 | USN-9065-1 |
| Ubuntu 22.04 LTS | glibc | 2.35-0ubuntu3.18 | USN-9065-1 |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | glibc | No fix yet | — |
| Ubuntu Pro 18.04 LTS | glibc | No fix yet | — |
| Ubuntu Pro 16.04 LTS | glibc | No fix yet | — |
| Ubuntu Pro 14.04 LTS | eglibc | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | glibc +220 | 2.39-145.el10_2 | RHSA-2026:84753 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | glibc +227 | 2.43-8.6.hum1 | RHSA-2026:69276 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | glibc +220 | 2.39-145.el10_2.alma.1 | ALSA-2026:84753 |
| AlmaLinux 9 | nscd +172 | 2.34-284.el9_8.4 | ALSA-2026:95618 |
| AlmaLinux 8 | nscd +213 | 2.28-251.el8_10.53 | ALSA-2026:96087 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | glibc | 2.39-145.el10_2 | RLSA-2026:84753 |
| Rocky Linux 9 | glibc | 2.34-284.el9_8.4 | RLSA-2026:95618 |
| Rocky Linux 8 | glibc | 2.28-251.el8_10.53 | RLSA-2026:96087 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | glibc | 2.38-150600.14.61.1 | SUSE-SU-2026:4656-1 |
| SLES 15 SP6 | glibc | 2.38-150600.14.61.1 | SUSE-SU-2026:4656-1 |
| SLES 15 SP5 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
| SLES 15 SP4 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
Show 13 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | glibc | 2.40-160000.7.1 | SUSE-SU-2026:23934-1 |
| SLES for SAP 15 SP6 | glibc | 2.38-150600.14.61.1 | SUSE-SU-2026:4656-1 |
| SLES for SAP 15 SP5 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
| SLES for SAP 15 SP4 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
| SLES 16.0 | glibc | 2.40-160000.7.1 | SUSE-SU-2026:23934-1 |
| SLE Micro 6.2 | glibc | 2.40-160000.7.1 | SUSE-SU-2026:23957-1, SUSE-SU-2026:23929-1 |
| SLE Micro 6.1 | glibc | 2.38-slfo.1.1_11.1 | SUSE-SU-2026:24281-1 |
| SLE Micro 6.0 | glibc | 2.38-159998.1.1 | SUSE-SU-2026:24326-1 |
| SLE Micro 5.5 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
| SLE Micro 5.4 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
| SLE Micro 5.3 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
| SLE HPC 15 SP5 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
| SLE HPC 15 SP4 | glibc | 2.31-150300.109.1 | SUSE-SU-2026:4591-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | glibc | 2.44-3.1 | openSUSE-SU-2026:12072-1 |
| openSUSE Leap 16.0 | glibc +4 | 2.40-160000.7.1 | openSUSE-SU-2026:21968-1 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | glibc | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | glibc +220 | 2.39-145.0.1.el10_2 | ELSA-2026-84753 |
| Oracle Linux 9 | nscd +214 | 2.34-284.0.1.el9_8.4 | ELSA-2026-95618 |
| Oracle Linux 8 | nscd +213 | 2.28-251.0.5.el8_10.53 | ELSA-2026-96087 |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | sln-2.43 +26 | 2.43-r18 | — |
| Wolfi rolling | sln-2.44 +26 | 2.44-r8 | — |
Advisories 22
- USN-9065-1 glibc vulnerabilities Ubuntu Security Notices (USN) · Nov 13, 2026
- WID-SEC-2026-3452 GNU libc: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Nov 12, 2026
- RLSA-2026:96087 Moderate: glibc security update Rocky Linux Security Advisories · Nov 10, 2026
- ALSA-2026:96087 Moderate: glibc security update AlmaLinux Security Advisories · Nov 10, 2026
- ELSA-2026-96087 Moderate: glibc security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Nov 9, 2026
- RLSA-2026:95618 Moderate: glibc security update Rocky Linux Security Advisories · Nov 6, 2026
- ALSA-2026:95618 Moderate: glibc security update AlmaLinux Security Advisories · Nov 6, 2026
- ELSA-2026-95618 Moderate: glibc security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Nov 6, 2026
- ELSA-2026-84753 Moderate: glibc security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Nov 2, 2026
- ALSA-2026:84753 Moderate: glibc security update AlmaLinux Security Advisories · Oct 29, 2026
- SUSE-SU-2026:24326-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 27, 2026
- SUSE-SU-2026:24281-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 27, 2026
- RLSA-2026:84753 Moderate: glibc security update Rocky Linux Security Advisories · Oct 20, 2026
- RHSA-2026:84753 Red Hat Security Advisory: glibc security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:69276 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- SUSE-SU-2026:4656-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 14, 2026
- SUSE-SU-2026:4591-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 9, 2026
- openSUSE-SU-2026:12072-1 glibc-2.44-3.1 on GA media SUSE / openSUSE Security Updates · Oct 9, 2026
- SUSE-SU-2026:23957-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 2, 2026
- SUSE-SU-2026:23929-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 2, 2026
- SUSE-SU-2026:23934-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 2, 2026
- openSUSE-SU-2026:21968-1 Security update for glibc SUSE / openSUSE Security Updates · Oct 1, 2026
References
- https://sourceware.org/bugzilla/show_bug.cgi?id=31026 issue-tracking
- https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0021 vendor-advisory
- https://sourceware.org/git/?p=glibc.git;a=commit;h=506ea57086bfb9ce3daff1c14246a1cb532aba0a patch
- https://joshua.hu/fuzzing-glibc-libresolv technical-description