Description
c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares' query-completion handling. The same flaw — a query's callback being invoked while the query is still linked in the channel's internal lookup structures — is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| c-ares | c-ares | >= 1.32.3, < 1.34.7 | — |
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 | c-ares | 1.34.7-1 | — |
| Debian 13 | c-ares | 1.34.9-1~deb13u1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.04 LTS | c-ares | 1.34.6-1ubuntu0.1 | USN-8844-1 |
| Ubuntu 25.10 | c-ares | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | c-ares +1 | 1.34.6-2.el10_2 | RHSA-2026:42096 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | c-ares +1 | 1.34.7-1.hum1 | RHSA-2026:36192 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | c-ares +1 | 1.34.6-2.el10_2 | ALSA-2026:42096 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | c-ares | 1.34.6-2.el10_2 | RLSA-2026:42096 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLES 15 SP6 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLES 15 SP5 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLES 15 SP4 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLES 12 SP5 | libcares2 | 1.9.1-9.24.1 | SUSE-SU-2026:3872-1 |
Show 12 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 16.0 | c-ares | 1.34.8-160000.1.1 | SUSE-SU-2026:23597-1 |
| SLES for SAP 15 SP6 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLES for SAP 15 SP5 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLES for SAP 15 SP4 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLES 16.0 | c-ares | 1.34.8-160000.1.1 | SUSE-SU-2026:23597-1 |
| SLE Micro 6.1 | c-ares | 1.34.8-slfo.1.1_1.1 | SUSE-SU-2026:23414-1 |
| SLE Micro 6.0 | c-ares | 1.34.8-1.1 | SUSE-SU-2026:23364-1 |
| SLE Micro 5.5 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLE Micro 5.4 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLE Micro 5.3 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLE HPC 15 SP5 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
| SLE HPC 15 SP4 | c-ares | 1.34.8-150000.3.29.1 | SUSE-SU-2026:4021-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | c-ares | 1.34.8-1.1 | openSUSE-SU-2026:11593-1 |
| openSUSE Leap 16.0 | c-ares | 1.34.8-160000.1.1 | openSUSE-SU-2026:21721-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | c-ares | 1.34.8-r0 | — |
| Alpine v3.23 | c-ares | 1.34.8-r0 | — |
| Alpine v3.22 | c-ares | 1.34.8-r0 | — |
| Alpine v3.21 | c-ares | 1.34.8-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | nodejs22 +4 | 1:22.23.1-1.amzn2023.0.2 | ALAS2023-2026-1981 |
| Amazon Linux 2023 | nodejs22-npm | 1:10.9.8-1.22.23.1.1.amzn2023.0.2 | ALAS2023-2026-1981 |
| Amazon Linux 2023 | nodejs24 +4 | 1:24.18.0-1.amzn2023.0.2 | ALAS2023-2026-1980 |
| Amazon Linux 2023 | nodejs24-npm | 1:11.16.0-1.24.18.0.1.amzn2023.0.2 | ALAS2023-2026-1980 |
| Amazon Linux 2023 | v8-12.4-devel | 3:12.4.254.21-1.22.23.1.1.amzn2023.0.2 | ALAS2023-2026-1981 |
| Amazon Linux 2023 | v8-13.6-devel | 3:13.6.233.17-1.24.18.0.1.amzn2023.0.2 | ALAS2023-2026-1980 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | fluent-bit | 3.1.10-7 | — |
| Azure Linux 3 | nodejs | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | c-ares +1 | 1.34.6-2.el10_2 | ELSA-2026-42096 |
Advisories 16
- WID-SEC-2026-2419 Red Hat Enterprise Linux (sssd, glib, c-ares): Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 10, 2026
- ALSA-2026:42096 Important: c-ares security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2026:36192 Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update Red Hat Security Advisories (RHSA) · Oct 6, 2026
- USN-8844-1 c-ares vulnerability Ubuntu Security Notices (USN) · Sep 29, 2026
- SUSE-SU-2026:23597-1 Security update for c-ares SUSE / openSUSE Security Updates · Sep 29, 2026
- SUSE-SU-2026:23414-1 Security update for c-ares SUSE / openSUSE Security Updates · Sep 14, 2026
- SUSE-SU-2026:4021-1 Security update for c-ares SUSE / openSUSE Security Updates · Sep 13, 2026
- SUSE-SU-2026:3872-1 Security update for libcares2 SUSE / openSUSE Security Updates · Sep 10, 2026
- SUSE-SU-2026:23364-1 Security update for c-ares SUSE / openSUSE Security Updates · Sep 10, 2026
- RHSA-2026:42096 Red Hat Security Advisory: c-ares security update Red Hat Security Advisories (RHSA) · Sep 4, 2026
- openSUSE-SU-2026:21721-1 Security update for c-ares SUSE / openSUSE Security Updates · Sep 2, 2026
- openSUSE-SU-2026:11593-1 c-ares-devel-1.34.8-1.1 on GA media SUSE / openSUSE Security Updates · Aug 26, 2026
- RLSA-2026:42096 Important: c-ares security update Rocky Linux Security Advisories · Jul 22, 2026
- ELSA-2026-42096 Important: c-ares security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Jul 21, 2026
- ALAS2023-2026-1980 Important: nodejs24 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Jul 20, 2026
- ALAS2023-2026-1981 Important: nodejs22 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Jul 20, 2026
References
- https://github.com/c-ares/c-ares/security/advisories/GHSA-6wfj-rwm7-3542
- https://github.com/c-ares/c-ares/pull/1237
- https://github.com/c-ares/c-ares/commit/1fa3b86a0b8d18fe7b60f3228a01d770feb026bc
- https://github.com/c-ares/c-ares/commit/d823199b688052dcdc1646f2ab4cb8c16b1c644a
- https://github.com/c-ares/c-ares/releases/tag/v1.34.7