# CVE-2026-59679: fs_read_glyphs() heap OOB read/write via encoding array index mismatch in libXfont2 CVE-2026-59679 is fixed in 5 products on 1 platform, first by SUSE-SU-2026:3500-1, released August 5, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-59679 - Priority: High - CVSS: 9.0 (Important) - EPSS: 0.0026 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Aug 5, 2026 - Weakness: Out-of-bounds Write - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-59679 ## Description fs_read_glyphs() in the libXfont2 font-server client (src/fc/fserve.c) indexes the per-character encoding[] array using num_chars from the FS_QueryXBitmaps16 reply, but that array was allocated with a size derived from num_extents in the separate FS_QueryXExtents16 reply. The two CARD32 fields are never cross-checked. A malicious or compromised font server can send a small num_extents (e.g. 1) in the extents reply, then a large num_chars (e.g. 100000) in the bitmaps reply. This causes attacker-controlled out-of-bounds heap read and writes. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | libXfont2 RHEL 10 | 2.0.6-5.el10_0.2 | [RHSA-2026:62123](https://patchblox.com/security/data/fix/linux/rhsa-2026-62123.md) | Aug 17, 2026 | | Linux | libXfont2 RHEL 8 | 0:2.0.3-2.el8_10.3 | [RHSA-2026:55446](https://patchblox.com/security/data/fix/linux/rhsa-2026-55446.md) | Aug 19, 2026 | | Linux | libXfont2 RHEL 9 | 0:2.0.3-12.el9_8.3 | [RHSA-2026:55447](https://patchblox.com/security/data/fix/linux/rhsa-2026-55447.md) | Aug 19, 2026 | | Linux | libXfont2 almalinux 10 | 2.0.6-5.el10_2.3 | [ALSA-2026:55448](https://patchblox.com/security/data/fix/linux/alsa-2026-55448.md) | Aug 17, 2026 | | Linux | libXfont2 almalinux 8 | 2.0.3-2.el8_10.3 | [ALSA-2026:55446](https://patchblox.com/security/data/fix/linux/alsa-2026-55446.md) | Aug 17, 2026 | | Linux | libXfont2 almalinux 9 | 2.0.3-12.el9_8.3 | [ALSA-2026:55447](https://patchblox.com/security/data/fix/linux/alsa-2026-55447.md) | Aug 17, 2026 | | Linux | libXfont2 amzn 2023 | 2.0.7-1.amzn2023.0.3 | [ALAS2023-2026-2112](https://patchblox.com/security/data/fix/linux/alas2023-2026-2112.md) | Aug 31, 2026 | | Linux | libXfont2 ol 10 | 0:2.0.6-5.el10_2.3 | [ELSA-2026-55448](https://patchblox.com/security/data/fix/linux/elsa-2026-55448.md) | Aug 17, 2026 | | Linux | libXfont2 ol 8 | 0:2.0.3-2.el8_10.3 | [ELSA-2026-55446](https://patchblox.com/security/data/fix/linux/elsa-2026-55446.md) | Aug 17, 2026 | | Linux | libXfont2 ol 9 | 0:2.0.3-12.el9_8.3 | [ELSA-2026-55447](https://patchblox.com/security/data/fix/linux/elsa-2026-55447.md) | Aug 17, 2026 | | Linux | libXfont2 opensuse-leap 16.0 | 2.0.7-160000.5.1 | [OPENSUSE-SU-2026:21539-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21539-1.md) | Aug 6, 2026 | | Linux | libXfont2 rocky 10 | 0:2.0.6-5.el10_2.3 | [RLSA-2026:55448](https://patchblox.com/security/data/fix/linux/rlsa-2026-55448.md) | Aug 17, 2026 | | Linux | libXfont2 rocky 8 | 0:2.0.3-2.el8_10.3 | [RLSA-2026:55446](https://patchblox.com/security/data/fix/linux/rlsa-2026-55446.md) | Aug 17, 2026 | | Linux | libXfont2 rocky 9 | 0:2.0.3-12.el9_8.3 | [RLSA-2026:55447](https://patchblox.com/security/data/fix/linux/rlsa-2026-55447.md) | Aug 17, 2026 | | Linux | libXfont2 sles 15.6 | 2.0.3-150000.3.6.1 | [SUSE-SU-2026:3500-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3500-1.md) | Aug 5, 2026 | | Linux | libXfont2 sles 15.7 | 2.0.3-150000.3.6.1 | [SUSE-SU-2026:3500-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3500-1.md) | Aug 5, 2026 | | Linux | libXfont2 sles 16.0 | 2.0.7-160000.5.1 | [SUSE-SU-2026:23151-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23151-1.md) | Aug 6, 2026 | | Linux | libXfont2-debuginfo amzn 2023 | 2.0.7-1.amzn2023.0.3 | [ALAS2023-2026-2112](https://patchblox.com/security/data/fix/linux/alas2023-2026-2112.md) | Aug 31, 2026 | | Linux | libXfont2-debugsource amzn 2023 | 2.0.7-1.amzn2023.0.3 | [ALAS2023-2026-2112](https://patchblox.com/security/data/fix/linux/alas2023-2026-2112.md) | Aug 31, 2026 | | Linux | libXfont2-devel RHEL 8 | 0:2.0.3-2.el8_10.3 | [RHSA-2026:55446](https://patchblox.com/security/data/fix/linux/rhsa-2026-55446.md) | Aug 19, 2026 | | Linux | libXfont2-devel RHEL 9 | 0:2.0.3-12.el9_8.3 | [RHSA-2026:55447](https://patchblox.com/security/data/fix/linux/rhsa-2026-55447.md) | Aug 19, 2026 | | Linux | libXfont2-devel almalinux 10 | 2.0.6-5.el10_2.3 | [ALSA-2026:55448](https://patchblox.com/security/data/fix/linux/alsa-2026-55448.md) | Aug 17, 2026 | | Linux | libXfont2-devel almalinux 8 | 2.0.3-2.el8_10.3 | [ALSA-2026:55446](https://patchblox.com/security/data/fix/linux/alsa-2026-55446.md) | Aug 17, 2026 | | Linux | libXfont2-devel almalinux 9 | 2.0.3-12.el9_8.3 | [ALSA-2026:55447](https://patchblox.com/security/data/fix/linux/alsa-2026-55447.md) | Aug 17, 2026 | | Linux | libXfont2-devel amzn 2023 | 2.0.7-1.amzn2023.0.3 | [ALAS2023-2026-2112](https://patchblox.com/security/data/fix/linux/alas2023-2026-2112.md) | Aug 31, 2026 | | Linux | libXfont2-devel ol 10 | 0:2.0.6-5.el10_2.3 | [ELSA-2026-55448](https://patchblox.com/security/data/fix/linux/elsa-2026-55448.md) | Aug 17, 2026 | | Linux | libXfont2-devel ol 8 | 0:2.0.3-2.el8_10.3 | [ELSA-2026-55446](https://patchblox.com/security/data/fix/linux/elsa-2026-55446.md) | Aug 17, 2026 | | Linux | libXfont2-devel ol 9 | 0:2.0.3-12.el9_8.3 | [ELSA-2026-55447](https://patchblox.com/security/data/fix/linux/elsa-2026-55447.md) | Aug 17, 2026 | | Linux | libxfont Debian 14 | 1:2.0.9-1 | [DEBIAN-CVE-2026-59679](https://patchblox.com/security/data/fix/linux/debian-cve-2026-59679.md) | Aug 10, 2026 | --- Data as of 2026-11-08T13:06:02Z UTC. 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